The base population for the recent study which is ayellow seed synthetic variety of maize was provided by Dr. M. Abd El-Sattar Ahmed, professor of crop science, Crop Science Department, faculty of Agriculture, Egypt.Two types of families had formulated, as a step before selection for high yielding ability. Those were half-sib (H.S) fami-lies and the first generation of self-pollination(S1) families. Variability in the base population gene pool had estimated depending on variance components of the families. The ratio of σ2A/ σ2G indicated that, additive genetic variance was more effective in controlling green and dry forage yield. This might indicate the importance of additive genetic vari-ance in maize population, consequently, selection among inbred- progeny would expect to be superior to other meth-ods under most genetic situations. Reduction in mean values of forage yield associated with selfing, reached 0.62 and 0.57 for green forage yield (Kg/ plot) and dry forage yield (Kg/plot), respectively. Values of genotypic variances estimated from S1 families were of larger magnitude amounted to 1.63 and 1.94 times the corresponding values for half- sib families in green forage yield and dry forage yield. Opposite to that, environmental variance estimates from S1 families were 0.56 and 0.55 of the respective values from half- sib families in green forage yield and dry forage yield respectively.Genotypic variations in term of coefficient relative to the overall mean of green yield and dry yield were less than 20%of the character mean when estimated from half-sib and S1 families (10.85 vs. 13.96 and 10.21 vs. 14.31% for green and dry forage, respectively).Dry forage yield expressed the highest estimates of heritability in both family types (0.829 and 0.877 for half –sib and S1 families, respectively). While, the obtained values for green forage yield were of lower magnitude (0.53 and 0.67 for half-sib and S1 families, respectively). This might indicate addition-al environmental influences with green forage yield.