About 55 of the cases involving primary pulmonary hypertension, or PPH, are eligible for trial, Wyeth said in a filing yesterday with the Securities and Exchange Commission. Lawyers representing former users and their families have sought to show that all the PPH cases meet the requirements to be considered by juries, the company said.

"Those numbers are scary," said Hemant Shah, an independent drug-industry analyst who has followed fen-phen litigation since 1999. "Forget about a billion for each case. Even if they only have to pay $10 million to settle them, that's still $3.5 billion. That's a significant amount of money for just PPH cases."

A Texas jury awarded more than $1 billion Tuesday to the family of a woman who died from PPH, a lung-shredding disease linked to diet-drug use. Wyeth had sought to resolve most fen-phen suits in a $3.75 billion nationwide settlement. More than 70,000 consumers have opted out of the accord to take their cases to trial. The drugmaker has set aside $16.6 billion so far for fen-phen litigation and has not ruled out adding to the reserve.

Shares of Wyeth, based in Madison, N.J., fell 48 cents to $38.01 in New York Stock Exchange trading. The shares have fallen 11 percent over the last year and 36 percent since fen-phen cases started going to trial in 1999.

More than six million prescriptions were written for the fen-phen diet combination before Wyeth pulled the drugs off the market in 1997 after researchers linked it to heart damage and lung disease. Consumers took the company's Pondimin or Redux drugs along with the generic phentermine to help suppress their appetites.

After the Texas verdict this week, Wyeth officials sought to reassure investors there were only a handful of PPH cases left to resolve. Plaintiffs' attorneys disputed that contention, saying they had hundreds of cases focusing on the fatal lung disease.

Of the 350 cases listed in its SEC filing, Wyeth said it expected 80 to be voluntarily dismissed and hoped to have a judge bar an additional 40 cases from proceeding because they did not meet standards for PPH cases outlined in the national settlement. The accord does not cover such cases.

A Philadelphia judge has set 92 PPH cases for weeklong, individual trials starting in August, according to court papers.

Wyeth's estimate that it faces only 350 PPH cases is low, said George Fleming, a Houston lawyer who represents former diet-drug users.

"I'd say there are probably less than a thousand," said Fleming, who is involved in the Philadelphia cases, "but there's certainly more than 350."