This study set out to assess the effect of publication of the British Guidelines on Asthma Management on the processes and outcomes of the inpatient care of acute severe asthma in the U.K. A criterion-based audit of all acute asthma admissions during August and September 1990 (immediately before) and in 1991 (1 yr after publication of the Guidelines) using eight criteria of process and outcome was performed. Thirty-six teaching and district general hospitals in England, Scotland and Wales took part. In total, 766 patients admitted in 1990, and 900 patients admitted in 1991, were studied. The 1990 and 1991 cohorts were very similar demographically and had asthma of comparable severity. Respiratory physicians achieved similar high performance rates of between 75 and 91% for seven of the eight criteria for both years. Respiratory physicians were significantly more likely to provide patients with a written management plan in 1991. General physicians' performance was significantly lower in both years, but overall there was a very small, but just significant, improvement in their performance in 1991. Some hospitals performed consistently well in both years. It is concluded that respiratory physicians consistently provide better asthma care than general physicians. Though statistically significant, the small degree of improvement was disappointing. Possible reasons include: insufficient time for the Guidelines to be incorporated into practice; inaccessibility of the Guidelines to general physicians; failure to accept responsibility for implementing the good practice reflected in the Guidelines; and an explicit need for strategies to implement the Guidelines beyond publication in a widely-read general medical journal.