A lack of consensus regarding the indications for total hip arthroplasty (THA) and total knee arthroplasty (TKA) has been cited as one reason for the variations in the rates of THA and TKA across the United States. The purposes of this study were to survey orthopaedists in a specific geographic area (New York City) regarding the candidacy of patients with osteoarthritis for THA or TKA and to compare indications for THA between orthopaedists at two academic medical centers, The Hospital for Special Surgery in the United States and McGill University in Canada. Orthopaedists were sent mail surveys asking about indications, factors affecting outcomes, and factors that might modify decisions for surgery. Approximately 45% of orthopaedists who performed THA and TKA in New York City in 1992 completed the surveys. Although there were wide variations among surgeons, most surgeons required at least severe pain daily, rest pain several days per week, transfer pain either several days per week (THA) or daily (TKA), and destruction of most of the joint space on radiograph. Younger age, comorbidity, technical difficulties, and lack of motivation modified the decision against surgery, whereas the desire to be independent and return to work swayed the decision for surgery. Most surgeons rated that patients with severe pain, osteoarthritis, or rheumatoid arthritis would have a high likelihood of an excellent outcome, whereas those with comorbidity and certain technical factors would have only a moderate likelihood of an excellent outcome. In the U.S.-Canadian survey of THA, in which more than 90% of surgeons responded, Canadian surgeons tended to require more frequent pain and use of assistive devices for walking. Although there was a majority of opinion for several indications, there was no clear consensus among surgeons regarding the indications for THA and TKA. Possible explanations for this are that isolated indications are not as important as integrating and weighing several indications and that the patient's desire to proceed with THA or TKA is an important driving force in the decision to operate.