A field experiment was conducted during winter seasons of 1988-90 to study the effect of irrigation and nitrogen on yield, protein and oil content in 'Sarama' Indian mustard [Brassica juncea (L.) Czemj. & Cosson] on sandy-lown soil. Three irrigations applied at 3 physiological growth stages (branching. flowering and seed development) gave higher seed yield (966 kg/ha) than 1, 2 or no irrigation. The increase in seed yield by 3 irrigations was 26.50, 17.08 and 54.86% compared with 1, 2 or no irrigation respectively. The crop responded favourably up to 80 kg N/ha under rainfed condition and up to 160 kg N/ha under irrigated condition. Irrigation and N increased the yield attributes, seed and oil yields, protein content and uptake of N in the seed. The response to N (each kilogram) and the returns/rupee invested on N fertilizer were the highest at 80 kg N/ha, followed by 160 kg N/ha.