The objective of the present research was to evaluate the percentage increase of oil and productivity of grains and their interrelations in two maize populations, through the estimates of genetic parameters as well as the study of the effects of one generation of inbreeding. Half-sib and S1 progenies from the same plant S0 were obtained and evaluated from two maize populations. The data for plant height and ear height were also considered. The studied populations were derived from "Composto Flint". The progenies were evaluated separately for each population in a lattice experimental design planted in a split block arrangement. The half-sib and S1 progenies means for the oil percentage were respectively, 5.31% and 5.19% for populations 01, and 6.21% and 5.63% for the population 02. For ear weight in population 01, the means were 4.68 and 2.91 respectively, for the half-sib and S1 progenies, and for the population 02, equal to 4.05 and 2.77 kg/5m². Although the means of the S1 progenies were always lower than those of the half-sib progenies, the analisys through the F test did not allow, at the 5% level of probability, to detect the effect of inbreeding depression in the means of the characteristics evaluated, except for the oil percentage in the population 02. The estimates of the genetic variancces among S1 progenies were higher than the estimates of the variances among the half-sib progenies, except for the ear weight in population 01 and ear height in population 02. The coefficient of heritability and genetic variation estimated, were lower in someway than those described in the literature when oil percentage is considered in both populations. For ear weight the population 01 showed a high value for the estimates of heritability (h² = 76.76%), on the other hand, the population 02 presented a low value (h² = 15.76%). The coefficient of additive genetic correlation between ear weight and oil percentage were -0.37 and 0.12, for the population 01 and 02 respectively. It was also concluded that, the selection carried out in population 02 in order to increase the embryo size, was effective to improve the average for oil percentage and also to break the negative genetic correlation between ear weight and oil content, however as a consequence of this type of selection a genetic variability reduction was observed for such characteristics.