Among 166 brands and varieties of cigarettes bought in the United States, Carlton 70s rank lowest in tar and nicotine content and Players are rated the highest, according to the Federal Trade Commission's latest cigarette ratings.

The FTC has been testing cigarettes and issuing periodic reports on the results since 1967, at the request of Congress. The latest report, released today, is the first since last November.

Levels of tar (defined as dry particulate matter) and nicotine (total alkaloids) were determined by testing samples purchase throughout the nation.

Regular-size, non-filter Players (hard pack tested at 34 milligrams tar and 2.5 milligrams nicotine, the highest rating for both components, and regular-size Carlton 70s filters were lowest at less than .5 mg. tar and less than .05 mg. nicotine.

Ranking after Carlton 70s as low tar and nicotine-content cigarettes were Carlton king-size filters, with or without menthol, and Now king-size filters (hard pack), also with or without menthol. Those four varieties all tested at 1 mg. tar and 1 mg. nicotine.

Others in the "top 10" ranking for low-tar and nicotine were Lucky 100s filters and Iceberg 100s filtered menthols, both with 3 mg. tar and .3 mg. nicotine. This was a reduction for both brands, which had tested at 9 mg. tar in November's FTC rating. Next were King Sano king-size filters, menthol and nonmenthol, both at 6 mg. tar and .3 mg. nicontine.True Kingsize filters, with and without menthol, tested at 5 mg. tar and .4 mg. nicotine.

Regular size nonfilter Players in hard packs tested at the highest levels of both components. Domino king size, nonfilters were next with 33 mg. tar and 1.4 mg. nicotine.

Other cigarette brands with high levels of tar and nicotine included the following:

Bull Durham king-size filters, 29 mg. tar and 1.9 mg. nicotine; half & half king-size filters, 26 mg. tar and 1.8 mg. nicotine; Herbert Tareyton king-size non-filters, 28 mg. tar and 1.8 mg. nicotine; and Chesterfield and Fatima king-size, non-filters, with 29 mg. tar and 1.7 mg. nicotine.

Americans smoked 620 billion cigarettes, or 31 billion packs, in 1976, according to U.S. Department of Agriculture statistics. That is 13 billion more than were smoked in 1975 and 84 billion more than in 1970.