The aim of this study was to analyse the association between factors characterising dairy herd management and the levels of somatic cell count (SCC), and total microorganisms count (TMC) in bulk tank milk. The investigations were carried out in 2005 in 187 family farms (herd size from 6 to 60 cows), situated in adjacent parts of Warmia & Mazury, and Mazowsze regions. Based on annual geometric means, all the farms were divided into those with low and elevated SCC level (<200,000 vs. 200,000-400,000 cells/mL), and with low and elevated TMC level in milk (<50,000 vs. 50,000-100,000 cfu/mL). The milk was characterised by low SCC level in 55 farms (29.4%), whereas TMC level was low in 65 farms (34.8%). The following factors were associated with the low level of SCC: small herd size, tie-stall system of cow housing, grazing cows, use of advisory service, use of antibiotics at cow dry-off, dry storing of milking clusters between milkings, post-milking teat dipping, regular use of California Mastitis Test, treatment of clinical cases of mastitis with antibiotics in selected cows only, use of whole straw in cow feeding, and use of salt-licks containing microminerals. Factors associated with the low level of TMC were: large herd size, colostrum feeding to the newborn calf by bucket, individual housing of replacement heifers older than 3 months, pipe-line system of milking, dry storing of milking clusters between milkings, pre-milking udder and teat cleaning with wet towel soaked with a disinfectant, tank system of milk cooling and storage after milking, and regular calculation of feeding rations for cows.