A study covering an area of 358 km 2 was conducted at Wami Plains in Mvomero district, Tanzania to assess the suitability of land for various land use types with emphasis on smallholder low input rainfed maize, rice and extensive grazing. Expert knowledge captured in ALES computer programme was used to carry out physical and economic land suitability classification with respect to three major land utilisation types. Decision trees to assess the potentials and constraints of the land for the three land utilisation types were developed in ALES programme. Physical and economic land suitability classification and ALES predicted yields and gross margins are presented. The results indicate that about 90% of the area is physically moderately suitable and economically highly suitable for extensive grazing. Only about 43% is both physically and economically suitable for maize production and about 57% is either marginally suitable or not suitable for maize production. On the other hand about 57% of the studied area is marginally suitable for rice production while 43% is not both physically and economically suitable for this LUT. The most limiting factors for the production of the three studied LUTs are poor soil fertility, poor soil drainage conditions, tsetse flies and ticks infestation and soil erosion hazards. From this study it is also concluded that extensive grazing is economically more profitable in the area compared to the production of maize and rice. Basing on the current farmers observed and predicted yields there are high possibilities for obtaining higher yields from livestock under improved management levels. Maize production is recommended as the second important LUT in the area provided that soil fertility problems and poor drainage conditions are improved. Rice production is economically the third land utilisation type. Higher rice yields could be obtained if farmers were able to invest more on fertiliser use. This forms a strong base in favour of high investment in the area given the potential marketing possibilities in the expanding cities and towns in Tanzania and in East Africa.