General and specialist services in public acute hospital outpatient departments play a key role in the health care system and represent a vital interface between inpatient and community care. Typically outpatient services involve millions of patient visits within a very short time frame and in Victoria alone between 8-10 million outpatient occasions of service are provided each year. Drawing on the first full year of data from the Victorian Ambulatory Classification System (VACS) this paper examines the patterns underlying the distribution of inpatient separations and outpatient encounters at 16 major Victorian public hospitals and assesses the relationship between inpatient and outpatient activity at the clinical specialty level.