Isosporosis in suckling piglets causes clinical and especially subclinical problems on many pig farms. During an organized screening, the diagnosis was made via faeces examination. In 83% of 63 herds with a possible history of isosporosis, oocysts were detected in on average 40% of the examined litters. Isosporosis was more frequently found on smaller farms and on the largest farms. Farrowing pens with full grids appeared to be less infected. The percentage of positive litters appeared to decrease with an increasing time interval between 2 consecutive sows in the pen. The routine disinfection methods after cleaning the pens appeared to have no effect. This screening mainly shows that coprological examination is an appropriate method to confirm the history of isosporosis on a pig farm.