The calculated profitability of using Bovine Somatotropin (BST) on typical dairy farms in The Netherlands ranges from Dfl.160 to 300 per cow per year, assuming 1985 prices and circumstances, and ignoring the costs of BST. A 20% increase in milk production and no change of the feed/milk relation were used for the calculations. BST is more profitable on intensive farms or on farms with more opportunities for alternative uses ofland, buildings and labour. The quota system, however, leads to a considerable reduction of profitability. At a national level, and with an unchanged milk price, a 28% adoption rate of BST would increase national income about Dfl.120 million. However, the cost ofBST or any decrease in milk price could reduce this amount, even to below zero. It is apparent that some dairy farmers who apply BST will earn more income whereas others will lose income.