OBJECTIVE To study the role of testicular fine needle aspiration (FNA) in the diagnosis of leukemia relapse. METHODS The study group consisted of 32 leukemia patients in complete remission for one to five years. Their ages ranged from 8 to 63 years. Twenty-five of them had bilateral testicular enlargement, and seven had unilateral enlargement. Hematologic workup and bone marrow studies of all of the patients showed no evidence of leukemia (full remission). FNA smears were obtained by using 22-gauge needles fitted to 20-mL syringes. RESULTS The smears revealed 13 cases of acute lymphoblastic leukemia L2 (ALL-L2), 8 of ALL-L3, 5 of acute monoblastic leukemia M5 (AML-M5), 1 of acute promyelocytic leukemia (APL-M3), 1 of AML-M1; 1 of erythroleukemia, AML-M6, 1 of chronic lymphocytic leukemia, 1 of chronic myelogenous leukemia and 1 of plasma cell leukemia. CONCLUSIONS FNA study of the testis is safe, time saving, rapid and easy to perform for the diagnosis of testicular leukemia relapse, obviating the need for biopsy.