Sirius Satellite Radio shares rose as much as 6.7% after the company yesterday said it surpassed a year-end goal of winning 1 million subscribers.

Shares of Sirius, the second-biggest pay-radio company, rose 31 cents to $8.26 at 1:15 p.m. New York time in Nasdaq Stock Market composite trading. Sirius’s share price retreated later in the day, closing at $8.10 for a gain of 15 cents. XM Satellite Radio Holdings, the biggest satellite-radio company, said it met its year-end goal of 3.1 million customers.

Holiday sales of portable receivers that customers can transfer from home stereos to autos boosted Sirius’s subscriber count, the company said. Sirius in October signed radio personality Howard Stern to a five-year contract beginning in 2006 that will cost $500 million and in November hired former Viacom Inc. President Mel Karmazin as its chief executive.

“There are no positive surprises,” said an analyst at Legg Mason Inc. in Baltimore, Sean Butson.” Sirius is up because the majority of the stock, about 70%, is owned by individual investors and they act on news that isn’t really news. As a result, you have to go to the chat boards to see what’s up.”

Butson has a “hold” rating on Sirius and a “buy” on XM Satellite.

XM Satellite shares fell 19 cents to close at $39.73 in Nasdaq Stock Market composite trading.

Neither XM Satellite nor Sirius, which offer nationwide digital signals, have posted a quarterly profit.

Sirius’s shares have more than doubled since the company signed Mr. Stern to a five-year contract Oct. 6. XM Satellite shares have gained 38% since then.

Sirius and XM Satellite are trying to lure customers to buy units in retail stores and persuade automakers to install receivers as factory options. The companies need more subscribers to pay for programming such as Mr. Stern’s show, said John LaForge, a fund manager at FA Asset Management in Sarasota, Fla.

Together, Sirius and XM Satellite “need 40 to 50 million subscribers to make the model work,” Mr. LaForge said. The subscriber counts announced today don’t “change the economics of the game.”

Mr. LaForge said he has shorted New York-based Sirius’s shares, betting the stock price will fall.

Sirius has invested at least $720 million in the last 12 months, including Mr. Stern’s show and a $220 million contract to broadcast National Football League games, for new programs to lure listeners. Mr. Stern’s current show on Viacom’s Infinity radio unit draws the biggest audiences among young men in Los Angeles and New York.

Sirius, which named Mr. Karmazin CEO on November 18, is paying him $1.25 million in annual salary plus bonuses for the five-year contract. He’ll also get 3 million restricted shares and options for 30 million more.

XM Satellite in October signed an 11-year, $650 million agreement to broadcast Major League Baseball games starting next year.

Sirius, which sells units at Best Buy and Circuit City Stores, can’t win subscribers fast enough to match spending unless it convinces automakers to install the radios in their cars at the factories, Mr. LaForge said.

“You’re not going to get enough people to install it” at Best Buy and Circuit City, he said.

“This result was due in part to a very strong reaction in retail,” said a Sirius spokesman, Patrick Reilly. “Advertising helped to drive this demand and our strong programming.”

Sirius in July said Ford Motor Company plans to have the company’s radios as a factory-installed option in some 2006 cars. Sirius also has exclusive partnerships with Daimler Chrysler AG and Bayerische Motoren Werke AG.

XM has been adding subscribers through its exclusive agreement with General Motors, the world’s biggest automaker. The company this month also signed an agreement with Toyota.

“We’ve had strong growth in both the retail market and in new car installations,” said an XM spokesman, Chance Patterson. “This year, about half of our subscribers came from the new car market and half from retail.”

XM has 130 channels and charges $9.99 per month. Sirius offers 120 channels for $12.95 a month.

“We’re very much in the early stages of satellite radio, and consumers are clearly willing to pay more for better radio,” said an analyst at Janco Partners in Denver, Colo., April Horace. Ms. Horace said she doesn’t own the shares, which she rates as “accumulate.”