SUMMARYCatecholamines produce a number of biochemical changes most of which result from stimulation of B,-receptors. Interest in these metabolic effects has increased recently as a consequence of the concern over the relatively high mortality from acute asthma attacks. In this review the data on the impact of P,-agonists on glucose production, insulin release and lipolysis are presented. Thereafter the subject of hypokalaemia, the mechanism for its production by p,-agonists and its relevance to cardiac arrhythmias are considered in detail. Finally the fall in plasma magnesium and the possible role of p,-