In 1994, 27.7 million surgical and nonsurgical procedures were performed during 18.4 million visits to ambulatory surgery settings. Eighty-five percent of the ambulatory procedures (23.4 million) were performed in hospital-based settings and 15 percent (4.3 million) were in freestanding settings. More than half of the ambulatory procedures were in three major categories: operations on the digestive system, the eye and the musculoskeletal system. The leading ambulatory procedures were extraction of lens (performed almost 2 million times), endoscopy of large intestine with or without biopsy (1.8 million) and insertion of prosthetic lens (1.6 million). Women had significantly more ambulatory surgery procedures than men. The ambulatory procedure performed most frequently on children under 15 was myringotomy. Also common for children were tonsillectomies and adenoidectomies. For those aged 15-44, frequently performed ambulatory procedures included endoscopies of large and small intestine; dilation and curettage of uterus; bilateral destruction or occlusion of fallopian tubes; and arthroscopy of knee. In the 45-64 year old group, endoscopies of large and small intestine were the most commonly performed ambulatory procedures. Extraction of lens and insertion of prosthetic lens were the leading ambulatory procedures for those 65 years and older, though endoscopies of large and small intestine were also performed frequently for this age group.