Aseptic foremilk samples of 213 cows from 77 small farms were collected. Of 852 samples, 65.5% were infected. The most frequently isolated pathogens were Streptococcus agalactiae (22.7%), Staphylococcus aureus (18.8%) and Staphylococcus epidermidis (18.3%). Somatic cell count (SCC, in thousand/ml) in foremilk samples, determined by Fossomatic, ranged significantly (P<0.01) between bacteria from 313' (non-infected) to 2128' cells/ml (infected by Streptococcus species). A high percentage of infected samples with no or weak SCC reaction was observed within all bacteriological findings. Thresholds of 120' cells, determined from a density distribution of SCC in uninfected an infected quarters, correctly detected 68% samples with 33 and 31% false negatives and false positives, respectively. Corresponding proportions at a threshold of 410' cells, estimated from healthy quarters were 55, 66 and 14%. The correlation coefficient between the SCC and the California Mastitis Test (CMT) was 0.61. For both SCC and CMT test the probability of misclassification for quarters infected with secondary pathogens was higher than those infected by streptococci.