This paper uses data from dairy farmers in six U.S. states to examine farm-level factors influencing the adoption of recombinant bovine somatatropin (rBST), a productivity-enhancing hormone that is injected in cows. The results of multinomial logit estimations of rBST adoption and disadoption show that herd size, education, and complementary technologies all play positive and important roles in rBST adoption.