This study attempts to evaluate the impact of farmland concentration on rural income growth among smallholder households in Tanzania. Conceptually, farmland concentration occurs when relatively few farms have relatively large shares of the arable land resources in a given area. Based on the pioneering structural transformation work of Mellor, Johnston and others, the distribution of productive assets in primarily agrarian areas might influence the strength of agricultural growth multiplier effects on both farm and off-farm economic activity and hence on household incomes. Land is the most important productive non-labor asset in rural areas of Sub-Saharan Africa. If large farms bring benefits that spill over to surrounding smallholders, then we might expect positive impacts of greater land concentration on household incomes. If, on the other hand, a small set of large farms dominates production, then growth multipliers may be lower than for areas with more egalitarian land distributions.