A randomized partial cross-over clinical trial of two intravenous techniques for outpatient conservative dentistry was performed in 61 patients. Subanaesthetic incremental doses of Althesin were used at 52 sessions and a single sedative dose of diazepam at 45 sessions. Each technique produced similar cardiovascular and respiratory changes. With Althesin, recovery after operation was more rapid and there was some evidence of a stronger anxiolytic effect and of less frequent and less severe thrombophlebitis. In contrast, Althesin was sometimes associated with jaw tremor or shivering and was less frequently mentioned by those patients who expressed a strong preference for one of the two techniques.