The objective of this study was to assess the frequency of testicular microlithiasis (TM) in infertile men who underwent testicular ultrasound and to determine any causative or associated factors. The case notes of 159 consecutive patients who were referred for testicular ultrasound in the investigation of male factor infertility were reviewed. Microcalcification was found in 10 cases (6.2%). This was unilateral in all cases and six patients had clinical evidence of a varicocele. Five cases had minimal calcification and five had marked TM. On patient had a past history of testicular maldescent and another of testicular torsion. Sperm function (as assessed by sperm count, motility and the sperm migration test) was variable within the 10 patients and there was no correlation with hormone profiles or testicular size. There was a statistical difference between a number of investigations in those patients with minimal degrees of calcification and those with TM (sperm migration test (SMT), namely sperm migration and sperm motility (p<0.05, Mann-Whitney U test)). The results showed a higher than expected incidence of TM. Patients with marked TM seemed to have poorer sperm function than those with minimal calcification. There was a high incidence of co-existing pathology, for instance scrotal varicocele and cryptorchidism, although the numbers in this study were small and further studies need to be carried out to determine the exact nature and significance of this condition.