Health problems encountered in the ambulatory setting differ from those of hospitalized individuals. For that reason disease classifications of morbidity devised for inpatient categorization are not totally applicable in the ambulatory setting. Numerous classification systems have been devised to overcome this discrepancy and have enjoyed varying levels of success. The International Classification of Health Problems in Primary Care (ICHPPC) is one of the more useful for family physicians and other primary care physicians. Its hierarchical structure and compatibility with the International Classification of Diseases (ICD) permits comparative use. The history, characteristics, and uses of ICHPPC are discussed as are those of additional classification systems recently developed for other purposes. One of these, a classification of performed procedures, may be used in conjunction with ICHPPC to provide a useful record for the provider as well as facilitating the referral of health-care information to third-party payors.