Conducted a longitudinal study of hypnotizability, as measured by the Stanford Hypnotic Susceptibility Scale, Form A, that yielded a relatively high degree of stability in hypnotic responsiveness over repeated testings spanning a 25-year period. The 50 Ss were retested in 1985, after tests when they were students, between 1958-1962 and again in 1970. The statistically significant stability coefficients were .64 (10-year retest), .82 (15-year retest), and .71 (25-year retest). The means did not change significantly, and the median change in the scores of individuals was only 1 point on the 12-item scale. A set of score measures and their intercorrelations are insufficient to resolve the issue of why stability occurs. The stability of hypnotizability over time compares favorably with that of other measures of individual differences.