Cancer therapy can further impair the already poor semen quality in cancer patients. This study evaluated the prefreeze and postthaw semen quality before treatment of patients with malignancies to examine the rationale for sperm banking for these men. Records of nine patients with different malignant tumors, who had been referred for sperm cryopreservation between 1982 and 1997, were reviewed and the results were compared with those of 50 normal healthy donors. Patients did not differ from donors in age, ejaculate volume, or duration of sexual abstinence. The total motile sperm count (median and interquartile range) was significantly different between patients and donors for prefreeze specimens (P = 0.026) and postthaw specimens (P = 0.008). Also, the percent motility was significantly lower in the patients as compared with the donors in prefreeze (P = 0.035) and postthaw specimens (P = 0.005). The percentage change in motility after thawing was also larger for patient samples (-54% versus -47%, P = 0.39). Other sperm motion characteristics did not significantly differ between the two groups except for postthaw curvilinear velocity (P = 0.01). This study concludes that fresh and frozen thawed semen from patients with malignant tumors is poor in quality but is still adequate for assisted reproductive techniques. As cancer therapy may further impair semen quality, patients should be offered the chance to bank sperm before undergoing cancer therapy.