Pollen viability and germination in vitro and in vivo were influenced by gamma irradiation for dosages of 0 (control), 100, 200, 300, and 400 Gy when this was applied to early and late trusses (1st-5th and 6th-10th) 4 times in a year (early spring, late spring, early autumn, and late autumn) in three cultivars of tomato (Lycopersicon esculentum) ('Gulle', 'Likya', and 'XPH5811'). The trial was carried out in 2003 and was repeated in 2004. Timing 1 was applied to flowers in trusses 1-5 (early spring, early autumn), and timing 2 to flowers in trusses 6-10 (late spring, late autumn). Exposure of pollen to high gamma doses, 300 and 400 Gy, resulted in the lowest rates of pollen survival and germination. Time of year and cultivar also had affects on pollen viability and germination rates. Viability and germination following exposure to gamma irradiation were not affected by the position of the truss on the plants. In situ pollen tube growth was recorded for all radiation dosages, pollen tubes of irradiated pollen were shown to grow successfully through the style and to enter the ovules.