Fine-needle aspiration cytology (FNAC) of the testis was done in 31 children (33 aspirates) with acute lymphoblastic leukemia (ALL) either as part of an end-therapy protocol (Group I, n = 20) or because of clinical suspicion of testicular relapse (Group II, n = 13). In Group I, none of the smears showed evidence of leukemic cells. However, two of these patients developed subsequent testicular relapse within 1 yr and were considered false-negative cases. Blast cells were present in nine patients of Group II; in the remaining four patients no neoplastic cells were observed in the smears and none experienced a relapse after a mean follow-up of 18 mo. Our findings indicate that FNAC can be a valuable method to evaluate clinically suspected testicular infiltration in children with ALL, and can be considered as an alternative procedure to surgical biopsy for screening testicular recurrence of childhood ALL.