It could be said that Melinda Konopko and Risa Meyer were born to do business together. They were, after all, born a day apart.

In both women’s lives, law and business cross-fertilize. Ms. Konopko’s father, Bruce Gould, is a lawyer who became a judge; Ms. Meyer is a lawyer by training. Ms. Meyer’s father, Alvin Meyer, helped start the mail order business in America; Ms. Konopko earned a master’s degree in business from Harvard University.

It could also be said that geography is part of their destiny: Ms. Konopko grew up on Central Park West, Ms. Meyer on Central Park South.

Finally, it could be said that business success is sometimes a matter of serendipity. Ms. Konopko and Ms. Meyer had never met, but when a mutual friend brought them together for tea in November 1998, they knew within the first five minutes that they would become business partners.

They now have one of the most successful Internet-based businesses in items for celebrations, PlumParty.com. From a 15,000-square-foot warehouse in Long Island City, they ship party supplies all across America and to dozens of countries in every part of the world.

“The Internet has so much depth that it gives the consumer not only choices but power,” Ms. Konopko said.

As it happened, the Internet’s commercial potential was just starting to be tapped when she met Ms. Meyer. After obtaining her Harvard MBA – and, earlier, a bachelor’s degree at Dartmouth College – Ms. Konopko worked at Dillon Read (now Warburg Dillon Read, a part of UBS) as an investment banker.

“One day, I realized that I really wasn’t interested in what I was doing as an investment banker, but that I was especially interested in every friend who had a product to sell,” Ms. Konopko said.

Separately, Ms. Meyer was coming to the same conclusion, albeit in her family’s jewelry business. She had joined it after graduating from the University of Michigan, and then obtaining a law degree at Yeshiva University’s Benjamin Cardozo School of Law.

“To start a business that offered party supplies through the Internet seemed natural to us,” Ms. Meyer said. “The dotcom era was booming, but the party entertainment business hadn’t quite embraced it. If you wanted to plan a good party, whether at home or at your office, you’d have to go to 10 different stores to get the right kind of supplies.”

An important business lesson that she’d learned from her father was that every product should be test-marketed diligently before being offered to the public. So Ms. Meyer and Ms. Konopko bought mailing lists from various catalogue producers, and created their own catalogue.

That initial test was hugely successful. The partners were featured on NBC’s “Today” show, and erstwhile hostess Katie Couric was so enthralled that she invited them again. National magazines ran articles on the two women and their enterprise. Orders started flowing in.

So did interest from venture capitalists.

“In 1999, venture capitalists seemed to be funding anything that had to do with the Internet – sight unseen,” Ms. Konopko said. “We knew of several entrepreneurs who got $50 million each without even a product to show. One potential competitor ran through $100 million in two months.

“Our view was different. We didn’t want VC funding because we didn’t want the pressure to show growth – no matter how unprofitable – that inevitably comes with that kind of funding. We wanted to build the business our way: slowly, methodically, and smartly.”

The partners, who had invested their own capital in the privately held company, certainly developed PlumParty.com smartly and methodically. But business growth was far from slow. Indeed, demand was such that they found themselves stocking more than 4,000 party-related items.

Those items covered more than 60 party themes. The themes tend to reflect various celebratory seasons: In late spring, for example, some of their customers throw parties to mark the big horse races, such as the Kentucky Derby. On June 6, many people hosted parties marking “6-6-6” – the sixth day of the sixth month of the year 2006.

As summer approaches, parties tend toward sun and surf. Halloween is another big theme.

Ms. Konopko and Ms. Meyer – who are both married, with children – say they enjoy enabling their customers to throw children’s parties, and weddings. On one recent day, they gave ideas to one customer throwing a baby shower in Los Angeles, and another putting on a square-dancing festival at a church in Idaho. One customer hosted a cemetery party – with black candles, skeleton napkin rings, and other ghoulish accouterments.

“The idea is to do something for a party that will make the guests laugh or gasp,” Ms. Meyer said. “Our supplies get people talking, and that loosens them up. We add energy to a party.”

Both partners seem genetically blessed with energy. Ms. Konopko’s mother, Karolyn Gould, is a well-known urban planner and social activist; Ms. Meyer’s late mother, Catalina Meyer, was active in the arts and entrepreneurship.

While the two partners have a keen eye for design and details, and provide original party material, they do not provide the catering. They make suggestions of vendors for food and special requirements, such as lights and music to help their customers create great events. They even have video Web logs on their site to give their customers hands-on ideas.

“We’re a one-stop shop,” Ms. Konopko said. “From themes to invitations to party supplies, our customers need not look beyond our business.”

The business is in the black, according to Ms. Konopko, although neither partner will disclose specific sales figures. Overall, the home-and-office entertainment business in America has annual revenues of $10 billion, according to the trade publication Party and Paper Retailer.

“The next two years will be about more growth,” Ms. Konopko said. “I feel that we’ve really hit our stride.”

What lies ahead may include accepting outside funding to expand the business.

“We wanted to wait until the right time,” she said.

Ms. Meyer added: “We didn’t get to where we are overnight. We did it the old-fashioned way – lots of hard work, determination, creativity, and good teamwork.”