Two mutant inbred lines of sunflower F 1 and F 2 hybrids derived after reciprocal crossings between those mutant lines were used to study seed shape inheritance pattern. Seed shape was evaluated as a length to width (L/W) ratio. One of the mutant lines had rounded shape of the seeds which length to width ratio was close to 1.0. Another line differed with elongated seeds with L/W ratio equal to 1.6'1.7. The length to width ratio of 1.4'1.5 in F 1 hybrids was intermediate as compared to its parents hybrid seeds being still elongated and differing sharply from the rounded seeds. F 2 populations showed two phenotypic classes in the shape of seeds with elongated seeds (L/W ratio>1.3) exceeding greatly rounded seeds (L/W ratio<1.3) in number. The used chi-square test indicated that the observed segregation corresponded to the theoretically expected both 15: 1 and 63: 1 ratios. The revealed segregations may indicate the control of the seed shape by two or even three unidirectionally acting genes. This implies that rounded seed shape is a double or triple recessive homozygote.