In arid and semi arid areas, water is the most limiting factor of crop pro -duction. Germination is susceptible to water shortage. Experimentation was undertaken to study the effect of water stress on germination of seeds of three sunflower genotypes (Oro 9, Mirasol and Albena). Six PEG 6000 osmotic constraints were tested (0, -0.4, -0.6, -1, -1.2 and -1.6 MPa). Results showed no significant difference between germination percent of the control and -0.4 MPa treatment and between -0.8, -1 and -1.2 MPa treatments. Germination percent was most reduced at -1.6 MPa (-65%). Mean germination duration was also affected and the highest value was obtained for -1.6 MPa (4.95 days, related to an increase of 185%). Differences between genotypes were significant in the treatment at -1 MPa.