A twenty-four-year-old trotter stallion had a swelling on the right side of
the scrotum for a period of one and a half years. None of the mares it ser
viced in the course of the last year of this period became pregnant. The sw
elling was identified as an infiltrative growing seminoma of the right test
is. The stallion was castrated unilaterally. One year after the operation,
the left testis was producing a small amount of sperm.