From weaning to death, 28 male Wistar rats were maintained on an ad libitum (AL) diet, and 24 counterparts were provided the diet every-other-day (EOD). The mean life span of the EOD group represented an 83% increase over that of the AL group. Furthermore, a Gompertzian analysis of mortality rates suggested that the rate of aging was retarded in the EOD group. While body weight and growth rate were reduced in the EOD group, their growth duration was 75% longer compared to the AL group. Significant positive relationships emerged between life span and growth rate parameters in the AL group; however, no significant relationships were found between life span and body weight parameters in the EOD group. Therefore, in support of the hypothesis that dietary restriction effects prolongevity through retarded development, evidence was produced only in the between-group comparisons of AL- and EOD-fed animals.