The variability of morphological and physiological characters among F1 animals from inbred lines is usually less than among the parental animals; it is questionable whether or not this generalization extends to variations in behavior. Attempts to deal with this question must take into account unequal variances and, ordinarily, a positive association between means and standard deviations in the parental lines. Comparing coefficients of variations does not in general resolve the problem. A method is suggested in which the variation is 1st transformed so that the regression of parental standard deviations on means passes through the origin, and coefficients of variation are then calculated on the rescaled variable. Application of this procedure to study on sexual behaviors in male guinea pigs suggests that the usual generalization regarding hypovariability among isogenic hybrids extends, at least, to these behaviors.