Four patients suffering from oligospermia and infertility were found to have slightly to moderately elevated serum prolactin levels consistently. Their testicular biopsy specimens showed varying degrees of impairment of spermatogenesis ranging from hypospermatogenesis to complete absence of germ cells. The usual known causes of hyperprolactinemia, such as pituitary or suprasellar tumors, hypothyroidism, intake of certain medications that deplete the dopamine levels of the hypothalamus or block the action of dopamine on the pituitary, were absent. These patients are described in view of recent clinical and experimental reports implicating hyperprolactinemia as a cause of male infertility.