The spontaneous locomotor activity (SLA) of 50 males and 50 females of Drosophila melanogaster has been recorded over a 12-h photophase once a week throughout their entire life span. In females, the SLA score regularly decreases with age. In males, the SLA score increases up to the 5th week of age and then decreases. In each sex, the correlation between the mean level of SLA displayed by the flies during their life and longevity was not significant. Less active flies are not the long-lived ones. This result is not in accordance with the rate of living theory.