Vietnamese agriculture is dominated by small - scale farm households. The diversified cropping system is common in northern Vietnamese agriculture. Farms have been transformed since independence, from self - sufficient systems that produced mainly rice, to div ersified farming systems, which now produce and market a large variety of products. The approach of this paper offers some other important innovations over previous Vietnamese studies. Data Envelopment Analysis is used to estimate technical efficiency and its components. Technical efficiency estimates are measured on diversified crops rather than individual crops. This is important because , a major challenge in examining production of farm households is crop diversification. The investigation of technical e fficiency should inform diversification policy for Vietnamese agriculture, especially from the base of rice production, and better understand the behaviour of farmers using land for annual crops. The results of this paper indicate the importance of crop di versification. Farms favouring market - oriented products, such as annual industrial crops, have greater efficiency than farms focusing on staple crops such as rice and maize. The results also suggest that there is technical and scale inefficiency among farm households in the North. Thus there is room to increase efficiency.