In December 1987 and January 1988 in a small station two of four boars showed a marked breakdown in the sperm quality. At the same time the mycotoxin ochratoxin A was identified in the feed at a concentration of about 8 ppb and in the bloodserum of 1 ppb. The relatively low toxin level seemed not to be due to the bad sperm quality, but considering the circumstances and the chronological course it might be an indicator for a higher toxic pressure, which may had happened a few weeks before. As other factors were not visible, most probably the feed must have caused a disturbed sperm production, which could be seen in all four boars. Whether ochratoxin A or other not identified mycotoxins can be hold responsible, could not be clarified. Therefore it is recommended to examine the effects of ochratoxin A on sperm quality of boars in future times.