A head feed combine was evaluated for optimization of combine parameters viz., cylinder speed (14.42, 15.53 and 16.64 m s-1), forward speed (3.5, 4.0 and 4.5 km h-1) and crop parameter viz., grain moisture content (18.1, 20.3, 22.4 per cent) in relation to threshing efficiency, cleaning efficiency and total grain losses for paddy variety CSR - 30. Moisture content of 18.2 per cent, cylinder speed of 15.53 m s-1 and forward speed of 4.0 km h-1 was found optimum for harvesting of paddy variety CSR - 30. Moisture content was the most important factor influencing threshing efficiency, cleaning efficiency and total grain losses followed by cylinder speed and forward speed.