The iMac accounted for 7.1 percent of all PCs sold by retailers in November and 8.2 percent of PC revenues, according to market researcher PC Data.
Last month's showing puts the iMac at the top of the heap since its August introduction.
``We can't deny it anymore - there is clearly an Apple buyer out there,'' said Roger Lanctot, PC Data's director of research.
``They are hungry and they are desperate, and Apple brought to market a package that was uncharacteristically competitive,'' he said.
The draw of the iMac was strong during the pre-holiday computer selling season. Sales of personal computers slumped earlier this year, but they've come back strong in time for the holidays.
While most computer makers are riding high, Apple's comeback from the depths has been especially sweet.
Since the iMac wowed U.S. consumers with its curvy design and its low $1,299 price, Apple's consumer market share has doubled to 10 percent, according to PC Data.
``It continues to surprise us,'' said Peter Godfrey, chief executive of Micro Warehouse, which sells more than $2 billion worth of computers through its MacWarehouse catalog.
While Apple remains America's No. 7 computer maker - trailing such giants as Compaq and Dell - its growth rate has soared in recent months and the company has at long last become profitable again.
Sales of iMacs are expected to reach 535,000 this year and should help boost Apple's profits in the latest quarter, which ends Friday. Wall Street is expecting Apple to earn 68 cents a share in the quarter, nearly double the 37 cents a share of a year ago.
The iMac's success now raises the question of what will be next for the company, since no PC maker can survive on one product alone.
``The challenge now is - can Apple play with a product line?'' asked PC Data's Lanctot.
The computer-maker is said to be hard at work developing a new, faster iMac with more features, which could be unveiled as early as next month.