The purpose of this study was to monitor changes in preoperative routines following recommendations given in 1989 by the Swedish Council on Technology Assessment and by the Swedish Consensus Conference on Preoperative Routines, both suggesting a more individualized utilization of preoperative testing. This was a multicenter, prospective, repetitive study conducted at seven Swedish hospitals providing surgical care. The subjects included all patients presenting at the operating theaters for surgical interventions requiring general or regional anesthesia. The main outcome measures were the frequency of reports of performed preoperative ECG, chest x-ray, and analysis of serum concentration of potassium. Before general recommendations were issued in 1989, 47% of the patients had had a preoperative ECG, 26% had had a chest x-ray, and in 61% serum potassium concentration had been measured. In 1991 these frequencies had been reduced by 5,6, and 9 percentage points, respectively (all figures given standardized for age and sex). Large differences were found between indidividual hospitals. Although recommendations suggesting a more restrictive and individualized utilization of preoperative testing have sparked important revisions in Swedish hospitals, there seems to be substantial potential remaining for further reduction of perfunctory use of preoperative screening.