the effects of different nitrogen amounts on maize yield were studied in three areas (bailundo, chianga and calenga) of the central highlands of angola and in two cropping seasons, dry season (june to september de 2005), with irrigation, and in rain season (october 2005 to may 2006). the assayed nitrogen levels were 0, 50, 100, 200, e 400 kg ha-1. the production of two maize varieties, the regional ？branco redondo？, and the imported ？zm521？ was assessed. the production was evaluated by the total weight of ears, the weight of 10 ears collected by hazard, the weight and the humidity of the grains of these ears. an analysis of benefits vs costs was done, considering the sell prices in the local market of the maize grain and the fertilizers costs, on the occasion of the trials.