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Water content of matured cotton leaves and petiols, from irrigation to wilting time, was determined in the fields of Torogh Agric. Station,Mashhad. The results show that both leaves and petiols moisture content decreases gradually as soil moisture is depleted. This decrease is more rapid near the permanent wilting time The leaf water potential was also measured and showed to increase from 12 bars in the day after irrigation to 35 bars in the time of wilting. Water content of petiol is consistently higher during moisture extraction. This suggests that petiols are reliable and useful indicators of constantly changing plant-soil moisture relatioship and therefore the time of irrigation.