The objective of this paper is to investigate the dynamics of the slaughter weight of Japanese beef cattle. We extend the theory of and provide empirical results for the dynamics of slaughter weight. Our theoretical analysis shows that optimal slaughter weight increases with an increase in the price of either feeder calves or the flow output while it decreases with an increase in either feed price or interest rate. Slaughter weight response to beef price depends on the sex of the animal. An increase in beef price is found to reduce slaughter weight of steers (male animals with no flow output); however, the result for slaughter weight of female animals is ambiguous. Our time series analysis for the Japanese beef sector (1975-1999) finds evidence of long-run relationships between the average slaughter weight and prices (except for interest rate), consistent with theoretical response patterns. However, the empirical results indicate that no specific relationships exist between the average beef slaughter weight and prices in the short-run.