Test-retest reliability data gathered from 79 sources (34 separate studies) were analyzed by a multiple-regression method in an attempt to estimate the effects of several factors on the temporal stability of individually tested intelligence. Five intelligence tests were examined: the Standford-Binet (except the fourth edition), the WISC, the WISC-R, the WAIS, and the WAIS-R. Samples encompassed a wide range of subjects divergent on status, age, and sample size. Subject age and status, gender, and test-retest interval were evaluated, and age and interval were found to be significant predictors of reliability. Subject sex and specific instrument were not found to have a significant effect on reliability. A summary table provides expected reliability coefficients, standard error, and percent of persons with IQ change in excess of 15 points, tabulated for combinations of each of the two predictors.