In order to evaluate the effect of irrigation regimes on yield and growth parameters of cumim [Cuminum cyminum L.] an experiment was implemented in Mashhad during the years 1998-2000. Six irrigation treatments were used as; T1: No irrigation during growing period (rainfed). T2: One irrigation during the flowering stage, T3: One irrigation during the seed formation T4: Tow irrigation during the growing season: one at the flowering stage and one at the seed formation, T5: Three irrigation during the growing season: one after germination, one at flowering and one at seed formation stage, and T6: full irrigation during the growing season. During The growing season, treatments of rainfed and full irrigation received 190 mm and 350 mm of water respectively. The resuets showed that by reducing numbers of irrigation in various treatments, plant water potential also decreased. It reached to-30 bars without showing any sign of witting in T1 as compared to-15 bars at T6-Seed yield the number of umbells per plant and the number of seeds per umbeI1swere not significantly different at 5 percent level of significance. However, treatment T6, showed to have the least weight or 1000 seeds and harvest index and highest total biomass. Differences between Height of 1000 seeds of 11 and harvest index in T3. T4, T5 and total biomass of T1, T2, T3, T4 with T6 were significantly different at 5 percent level. The overall results of one year experiment showed hat in Mashhad climatic condition, cumin doesn't need to be irrigated in normal years.