Fourteen genotypes and 3 different gamma ray doses were tested to develop an efficient haploidization protocol in squash. For this purpose, male flowers collected 1 day before anthesis were irradiated with 150, 200, and 300 Gy gamma ray doses, and female flowers were pollinated with the irradiated pollens the next day. In the first year of the study, 1858 embryos were obtained from 219 fruits. While 1358 of these were found in fruits irradiated with a 150 Gy gamma dose, the remaining 500 embryos were found in fruits irradiated with 200 Gy. From fruits irradiated with 150 and 200 Gy gamma doses, 9.12 and 3.53 haploid embryos per 100 seeds were obtained, respectively. While Genotype 3 was the most successful genotype with 12.42 embryos per 100 seeds, the minimum embryo numbers were obtained from Genotype 4 with 1.46 embryos per 100 seeds. In the second experimental year, 8 genotypes and the same gamma doses were used, and 2625 haploid and 1378 diploid embryos were obtained from 217 fruits. At irradiation doses of 150, 200, and 300 Gy, 2010, 539, and 76 haploid embryos were found, respectively. Genotype 6 was the most successful genotype with 13.35 embryos per 100 seeds. © Tübi̇tak.