This study was performed to compare the efficiency of different colchicine application methods for doubling of haploid melon plants in melon breeding programs. Doubled haploids assist breeding by reducing time for the recovery of homozygous breeding lines. Irradiated pollen technique provides successful results in melons and pure breeding lines can be produced in relatively shorter time. Despite the advantages, low frequency of haploid embryos, difficulties for detecting and excising the embryos and low percentage of duplication rate are the limiting factors of this technique. The objective of this study was to determine the effect of different colchicine treatments to double haploid melon plants. The same dose of colchicine (0.5 %) was applied either in vitro or in vivo and the resulting doubled haploids were compared. The results indicated that the most convenient method was found in vivo application of colhicine (0.5 %) by shoot tip immersing method for 2 hours. The mean duplication rate was 10.13 % after in vitro colchicine application and 46.03 % after in vivo colchicine application among the genotypes of 'Kirkagac' and 'Yuva Hasanbey melon groups.