The prevalence of Toxocara vitulorum in cattle around Bursa, Turkey, was surveyed by faecal examination of eggs. The average infection rate among 11 towns was 5.1% in calves younger than 6-months-old, and 2.2% in all ages of animals. T. vitulorum was found to be prevalent in two different areas of Bursa. Third stage larvae were found in one milk sample and therefore galactogenic transmission was suggested. Experimental incubation of eggs showed that the optimum temperature for development was 20 to 30-degrees-C and eggs could survive under low temperature, indicating that grazing in the contaminated pasture may accelerate the transmission of eggs to cows. Mode of farming, therefore, affects the infection rate of T. vitulorum and may explain the difference in the rate between the two areas.