Abstract: A field experiment comparing different drip irrigation regimes and plant arrangements on potato yield and its component, leaf, stem and total dry matters, harvest index and water-use efficiency was carried out in a clay soil. This study was carried out on the experimental Farm of Ardebil Agriculture Research Station in 2006. The experiment included three treatments for different drip irrigation regimes: I1 (full irrigation), I2 (80% of full irrigation), I3 (60% of full irrigation) and three treatments for plant arrangements: conventional cultivation (P1), two rows 35 (P2) and 45 (P3) cm apart on a wide bed 150 cm. Results indicate that both drip irrigation regimes and plant arrangements didn’t influence the harvest index. In all varieties, I1, I2 and I3 produced the lowest amounts, respectively. Plant arrangement hadn’t significant impress on tuber yield, numbers and average weight of tubers. P3 and P2 treatments produced maximum and minimum values in more characteristics. The yield of tuber, leaf, stem, total and harvest index indicated increasing trend during the harvest times and only the stem and leaf yield decreased at the two final harvests. In most variables interaction effect of the (I1xP3) generated. Accumulative amounts of reference and 100, 80 and 60% crop evapo-transpiration (EP) were 782.2, 627.6, 502.0 and 376.5, respectively. Water Use Efficiency (WUE) with increase water supply improved. Treatment of I1xP3 had the highest WUE. Its values during growth period increased and maximum WUE obtained at 109 Day after Planting (DAP).