Effect of harvest date on seed viability has been examined in 3 different sunflower genotypes. Harvesting started 7 days after fertilization. It was done 10 times, at 3-4-day intervals. Seed moisture was determined before each harvest. Trials were conducted in India and Serbia. Seed viability was determined 3 months after the harvest. Genotype ranking regarding seed viability, was not the same in the two locations; higher average seed germination was registered in Serbia. There were no significant increases in seed viability once the average seed moisture at the time of harvest reached 41% (India) and 48% (Serbia). Differences existed between the locations in minimum and maximum daily temperatures. Regression analysis showed that highest seed germination rates were reached when seed moisture content at harvest went below 32%, in most cases when seed moisture reached 22-23%.