As a nurse, Royanna Commisso is well-versed in the health benefits of dermatological checkups. But she never made time for an appointment until her employer, Merrill Lynch, hired a dermatologist to conduct skin screenings at its in-house health clinic.

That was in 2005, and today, Ms. Commisso, 63, is thankful for the exam, which turned up basal cell carcinoma. Doctors found cancer again in 2006, when she was screened a second time at the clinic, on the third floor of the company’s headquarters at 4 World Financial Center.

“Every year our screenings, especially dermatology and mammography, pick up at least one cancer,” Ms. Commisso, the director of medical services at Merrill Lynch, said. Employees like that appointments are so convenient, she added. “I would be one of those people … I honestly don’t think I would have taken the time and made an appointment, and I’m a nurse.”

Tapping into their employees’ hectic schedules, large corporations increasingly are using on-site health clinics to promote wellness and, by extension, stem the costs associated with unhealthy employees who miss work for doctors’ appointments or are not productive when they come in feeling ill. While companies have offered health services for years, some are expanding them to include specialized care such as mammograms, blood pressure checks, allergy shots, physical therapy, and prescription delivery.

At Goldman Sachs, a program to promote employees’ overall health, the Wellness Exchange, includes access to on-site fitness centers, nutrition programs, and health services, and is staffed by 15 medical professionals. “The mission is really to build an environment that supports wellness for our people,” an associate in the human capital management department, Lilly Maisel, said.

Services including physical therapy are driven by employee needs, she said. “We’re constantly trying to accommodate the new needs of employees. We are looking to bring an orthopedist on site. We don’t have an X-ray machine, but we know we need one,” she said.

In recent years, the focus at on-site health clinics has shifted to promoting health, a clinical researcher at Columbia University’s Mailman School of Public Health, Robyn Gershon, said. “Let’s face it, most adults are working, and it’s a great way to reach them in terms of health care,” she said, adding that the main focus for many corporations is cardiovascular health. “It’s always finances that drive these things, and there seems to be some real cost savings when you can treat and prevent these chronic illnesses.”

Typically, salaries for doctors at the clinics are competitive, and in most cases employee health insurance plans pay for care.

At the New York Stock Exchange’s clinic, the staff arrives an hour before the market opens and remains on hand for an hour after it closes. For $60, the clinic, which is run by a Virginia-based company, Comprehensive Health Services, offers hearing and vision tests and echocardiograms, among other services. It sees about 50 patients a day. “We have a captive audience,” the head nurse, Rosalyn Hochberg, said. “If you come see me and your blood pressure is a little high, I’ll send you to a doctor. It’s easy, two seconds.”

Ms. Hochberg said the setup is cost effective. “If you come here on a sick call, you don’t have to take any time off. We take care of you, you go back to work,” she said.

Still, on-site care is not likely to replace outside doctors’ visits anytime soon, mostly because of privacy concerns. “It has its limits,” Ms. Gershon said. “Would you want to go to your practitioner if you have a drug problem?”