The analysis of input use pattern and returns of paddy in selected agricultural systems during 1997-98 in Tungabhadra Project (TBP) area, Karnataka clearly revealed that the per hectare expenditure on plant protection chemicals and chemical fertilizers were the major components of total cost of paddy cultivation in both Highly Intensive Agricultural System (HIAS) and Semi Intensive Agricultural System (SIAS). However, expenditure on fertilizers and plant protection chemicals was lower in paddy under Ancient Irrigated Agricultural System (AIAS). In AIAS, the per hectare expenditure on human labour formed major components of paddy cultivation. The net returns of kharif paddy was found to be higher in AIAS (Rs.19,890.89/ha), compared to HIAS (Rs.17,256.07/ha) and SIAS (Rs. 14,291.84/ha) mainly due to lower cost on plant protection chemicals and fertilizers in AIAS. Though the cultivation of paddy in SIAS and HIAS were found intensive, their profitability were found to be lower than that of AIAS.