Anti-HTLV-I antibody was measured in 69 cerebrospinal fluids (CSFs) of cases with typical HTLV-I associated myelopathy (HAM) and other disorders whose symptoms were similar to HAM in order to evaluate the diagnostic significance of anti-HTLV-I antibody in CSF. Both gelatin particle agglutination (PA; Serodia-ATLA) method and recombinant gag-env hybrid protein coated ELISA were employed simultaneously. Antibody titers of both methods showed linear correlation. Cases with typical HAM (24 cases) and HAM with additional neurological manifestations (7 cases) showed high positivity in both methods. Cases with other neurological disorders with possible HAM (11 cases, seropositive) and cases with other neurological disorders without HAM (12 cases, seropositive) showed low positivity with low titer in ELISA, on the other hand, 81% and 67% of those cases were positive in PA method. All cases with seronegative neuroimmunological disorders (15 cases) were negative in CSFs. These findings showed that anti-HTLV-I antibody in CSF is significant in diagnosis of HAM, and both PA and gag-env ELISA are useful to detect anti-HTLV-I antibodies in CSF.