The inheritance of tail length and spine length was estimated using 2667 Merino lambs measured at approximately 6 weeks of age on the marking cradle. Maternal permanent environmental effects affected spine length and marking weight but not tail length. The heritability of tail length and spine length was both 0.58 ± 0.05, while the genetic correlation between the two traits was 0.58 ± 0.05. However, adjusting the data for marking weight or spine length removed the genetic correlation between spine and tail length. The heritability of a subjective score for tail length was 0.38 ± 0.05. The results indicate that selection for short tails is possible and that it will not have a negative impact on spine length provided adjustment is made for body weight or spine length.