This publication on the genetics and breeding of dairy cattle in the tropics is concerned with the crossing of Bos indicus and Bos taurus. It contains a re-evaluation of published papers on the subject from all parts of the tropics. It integrates and reinterprets the results globally and draws conclusions on the ideal combination of indigenous with temperate genes. It examines genetic models of the additive-dominance type. It evaluates the contributions of additive and heterotic effects and their interactions with levels of management and environment. Suggestions are made on the most efficiency design of future research on this topic and breeding plans for project development are proposed