MSc. DissertationThe evidence over a negative relationship between farm size and productivity in large global literature is largely dependent on a narrow range of farm sizes excluding medium and large scale farms. This study was carried out to determine the relationship between farm size and agricultural productivity over a wider range of farm sizes across maize cropping systems in maize producing districts of Tanzania Mainland. Specifically, the study attempts to: (i) estimate the farmers‟ total factor productivity level across maize cropping systems, (ii) determine the relationship between farm size and total factor productivity level across maize cropping systems and (iii) identify factors other than farm size which influence agricultural productivity across maize cropping systems in the study districts. OLS Regression technique was employed to determine the relationship between farm size and the level of total factor productivity. Data for the study comprised of 1001 observations randomly selected from ASPIRES Project data set of 1200 observations comprising of small, medium and large scale farms. The data were collected during the 2015/16 cropping season from eight maize producing districts namely Mvomero, Kilombero, Njombe, Kiteto, Magu, Moshi Rural, Mkuranga and Liwale in Tanzania Mainland. The findings indicate variation in the level of total factor productivity (TFP) across maize cropping systems, ranging from 1.22 for maize-pure stand and 1.64 for maize-legumes intercropping systems. Contrary to the evidence in favour of inverse relationship between farm size and productivity, the regression results in this study indicate a significant and positive relationship between farm size and total factor productivity level across maize cropping systems. Moreover, other factors including household size, land slope, source of water and measurement errors had significant influence on the farm-level productivity across farm size categories and cropping systems. The study recommends review of the existing agricultural related policies,strategies and/ or programmes to ensure that medium and large scale farms are also promoted instead of the currently emphasis on smallholder-lead agricultural growth as pathway to economic development in the country. Also the following are recommended in order to improve agricultural productivity and hence increase marketable surplus which is essential for ensuring adequate supply of raw materials for the agro-industries as the country is striving to become an industrialized and middle income country: (i) Review of the National Agriculture Policy 2013 and the Agricultural Sector Development Programme (ASDP II), (ii) Promoting land productivity enhancing mixed cropping systems, (iii) Promoting family planning strategies and actions, (iv) supporting low-cost irrigation strategies and programmes, (v) hastening the process of formalization of land rights and (vi) providing education on and promoting appropriate farming practices on hilly/high slope land.