The atrioventricular conduction time (P-R interval) was determined in 189 women and 90 men with rheumatoid arthritis (RA). Only three women and one man were found to have pathological prolongation of the P-R interval. However, a significant prolongation of the P-R interval, within normal range, was seen in women with RA compared with healthy controls. Apart from the relation to radiographically enlarged heart, prolonged P-R interval showed no association with other signs of RA and had no prognostic implications in the follow-up period (mean 5.4 years). Current chloroquine therapy delayed the atrioventricular conduction while corticosteroids accelerated it.