Research carried out by the Forage Research Institute Iregszemcse in 1995 revealed diversity in dynamic of achene dry matter accumulation (DMA) of sunflower hybrids by growth analysis. Twelve different hybrid genotypes (produced by factorial mating of 3 cms lines and 4 restorers) were planted in a randomized complete block design. During the period of maturity achene samples (six times at 7-day intervals, 5 heads per hybrid) were collected. Growth curves, equations and bRGR were computed on the basis of a special formula, InY = Po + P1X + P2X2. In this case, relative growth rate (RGR) is a linear curve (RGRy = P1 + 2P2X). Consequently, the curve of RGR is possible to be characterized by the coefficient of the variate X. 2P2 = bRGR. Coefficient bRGR defines the speed of the growth process. Achene dry matter accumulation can be described precisely by this model, because the cubic component was not significant. There were clear differences among DMA, absolute growth rate (AGR) and RGR of genotypes. The effect of parental lines on bRGR was computed by the analysis of variance in M x N table (M = cms lines, N = restorer lines) without replications. Significant effect of cms lines on bRGR was detected. Results indicate that the speed of DMA, which is measured by bRGR, is an important heritable character of sunflower.