In the investigation of patients with hypertension, we have performed a large number of ambulatory recordings of intra-arterial pressure. Subjects were encouraged to behave as normally as possible, being little encumbered by the monitoring apparatus, and several had sexual intercourse during the recording period. We report here the heart rate and blood pressure changes during coitus in these subjects and also in two subjects monitored specifically to investigate symptoms related to coitus. Results from a subject who had coitus during an inital study and also during a restudy after treatment with a beta-adrenoceptor blocking agent are also reported. The monitoring equipment consisted of a revised version2 of a system initially developed in Oxford.' A cannula was inserted percutaneously under local anaesthesia into the non-dominant brachial artery of the subject and joined by fine-bore tubing to a transducer/perfusion device. Signals from this and from adhesive chest electrocardiographic electrodes were recorded on two channels of cassette tape using a miniature recorder ("Medilog", Oxford Medical Systems). Enough wire was provided to allow the subject to position the recorder either behind him or at his side when lying flat. No event-marking system was used during these recordings but the time of occurrence of intercourse was recorded in the subject's diary. The system was calibrated each morning and evening during the recording.In accordance with our standard procedure all tapes were written out in full using a pen-recorder (Lectromed). Episodes of sexual activity were easily identified and later replayed at faster paper speed using a fibreoptic recorder (Medelec Ltd). The nearest calibration signals were written out using the same system 3n an identical setting. The mean blood pressure and heart rate during the one minute before fluctuations associated with sexual activity were taken as precoital recordings and the highest levels sustained for five or more beats as "peak coital" values. Results

1 The antihypertensive activity of the diuretic xipamide has been studied in 18 patients with mild/moderate essential hypertension using the technique of continuous ambulatory intra‐arterial blood pressure recording. Full data from 48 h blood pressure recordings before and after treatment were available from 13 patients. 2 After a mean period of 3 months' treatment with xipamide 20 mg once daily, both systolic and diastolic blood pressure were markedly reduced throughout the whole 24 h day, the reductions of systolic being statistically significant throughout the whole period, and of diastolic for 19 out of the 24 hourly periods measured. There was no postural hypotension seen during treatment and there was a conspicuous lack of side effects. 3 Xipamide would appear to be as effective as many beta‐adrenoceptor blockers but without their side effects and produces a better control of blood pressure throughout the whole day and night.