A quantitative and qualitative evaluation of microbial contamination of harvested colostrum on 39 Czech dairy farms. The study identified the proportion of colostrum samples that met the recommended goals for total plate count (TPC), total coliform count (TCC), and gramnegative noncoliform count (NCC), and evaluated the effect of the farm, breed, parity, season of the year, time of calving, and colostrum volume on these 3 microbiological parameters. Colostrum samples (n = 1,241; 57.6% from Czech Fleckvieh, and 42.4% from Holstein breed) were collected on dairy farms between 2015 and 2017. The samples were collected after the first milking. In 155 out of 1,241 colostrum samples the species of microorganisms obtained by culture were determined, and the findings were classified into 4 groups: (1) normal inhabitants of bovine skin and mucosa, (2) fecal contaminants, (3) environmental contaminants, and (4) potential gram-positive mammary pathogens. Results showed heavy microbial contamination (TPC median = 408,000 cfu/ mL; TCC median = 200 cfu/mL; NCC median = 80 cfu/mL). Only 28.4% of samples met the requirement for TPC ( < 100,000 cfu/mL), 88.2% for TCC ( < 10,000 cfu/mL), and 86.0% for NCC ( < 5,000 cfu/mL). Among the tested factors, farm had a significant effect on all 3 microbiological parameters, volume of colostrum had an effect on TPC (the highest TPC in < 3.0 L of colostrum), and season had an effect on TCC and NCC. The most of microbes isolated from colostrum belonged to normal inhabitants of bovine skin and mucosa, fecal, or environmental contaminants. Potential gram-positive mammary pathogens were found in 13.5 % of samples. Escherichia coli was isolated from 9.0 % of colostrum samples, and Streptococcus uberis and Streptococcus parauberis were each isolated from 5.2 % of samples. Our study showed high microbial contamination of colostrum collected on dairy farms. Therefore, better hygiene and sanitation around colostrum harvest should be addressed by farmers