The metabolic effects of a widely used betamimetic agent (ritodrine) were studied in two groups of pregnant patients with abnormal glucose tolerance. No significance modification of various metabolic parameters was detected when the drug was orally administered in standard doses for at least 1 week. The possible reasons for this finding are discussed. Following the absence of any diabetogenic effect, a prolonged use of betamimetics to achieve tocolysis seems to be safe even in patients with metabolic disorders.