A production function describes the technical relationship that transforms inputs into outputs. In agriculture, one model used to measure this relationship is Cobb-Douglas production function. This model is chosen for its simplicity and the way it helps to estimate the returns to scale. This function was estimated to identify the determinants of agricultural production and to measure the returns to scale recorded in agriculture sector in Rwanda. As for the profitability, the gross margin and the net farm income were computed for different crops (beans, cabbage, corn, Irish potato, onion, tomato and wheat) grown in Rwanda.