The role of agriculture in economic growth and the wider structural transformation of Tanzania is a key concern for policy-makers. This paper tries to understand time trends in agricultural productivity. The main finding is that the most important source of consumption growth in Tanzania between 1991 and 2007 has been structural change, i.e. people moving out of agriculture. Within the smallholder agricultural sector, yields of the most important crop – maize –have been declining during the 2000’s, and total factor productivity and adoption of technologies such as improved seeds and inorganic fertilizer have been stagnant at best.