Nine sorghum mutant lines as well as the parental variety Giza-l were evaluated at three irrigation intervals. i.e.. 10. 20 and 30 days during two seasons. Forage and grain yield data were subjected to phenotypic stability analysis according to the procedure proposed by Eberhart and Russell (1966). The results indicated that the three autant lines No. 15. 17 and 21 were more stable than the autant line No. 32 under the studied envi ronaental study. The unstable line No. •32 seemed to have high grain yield above grand mean. This line. however, could be over looked because their high yield potential was limited to particular environments, This autant line No. 32 gave the highest grain yield when irrigated every 10 days.