Income inequality has been rising in parallel with the economic liberalisation process in the former centrally planned economies, though the contribution ofthe agricultural sector to this rising inequality is not clear. Factors such as there distribution of land and the opportunities for non-agricultural income fromthe market liberalisation process would seem to be important in determining inequality within this sector. This paper reviews the trends in rising inequality in the former centrally planned economies in general examining differential trends and hypothesised causes. It presents inequality measures for one District in northern Vietnam, showing that non-agricultural income sources,specifically aquaculture, contribute more to present inequality than any other income source. Simulation shows that the emergence of aquaculture since thelate 1980s has been driving the inequality increase in that period. Inequality isimportant because of its relationship to other factors in the evolution of the agricultural economy such as the incidence of poverty and long term environmental sustainability. In the context of a wider research project onsocial vulnerability to environmental change, of which this paper is a part,rising inequality in the case of northern Vietnam, signals an increase in baseline social vulnerability to extreme climate events and to climate change.