as a first step in a program of evaluation of ground beef microbiological quality in the city of piracicaba, sp, forty samples of ground beef were taken at two kinds of retail markets (meat shop and supermarket), related to an old and a new system of meat merchandising. the samples were taken weekly in the morning and in the afternoon, during a two month period. total bacterial counts were determined by a procedure recommended by the american public health association and plates were incubated at 21oc (72 hours) and at 32oc (48 hours). the results can be summarized as follows = 1) total counts were generally high, with several samples in the range 107 to 109 cells/gram; average counts were 6.9x 107 cells/gram (21oc) and 2.5xl07 cell/gram (32oc). 2) incubation at 21oc resulted in total counts generally higher than those found at 32oc, although there was no statistically significant difference between the two incubation temperatures. 3) total counts were found to be higher in samples from the small shop (old system) than in samples from the supermarket (new system); the difference was related to higher counts in the morning samples taken at the former retail market.