Although consultation, as an activity for intervention, has achieved considerable popularity among human service professionals and figures prominently in current federal mental health legislation, a basic question still unanswerable is, "Does it work?" This paper reviews 35 consultation outcome studies reported between 1958 and 1972 in an attempt to provide some answers to this question. Although their quality varies greatly, the evidence seems to lend some support to the effectiveness of consultation as a change method. In 69% of the studies reviewed, positive change was demonstrated on the consultee, client, or system level or at some combination of these. The review also suggests that, despite a need for studies which build cumulatively on earlier ones so as to provide comparable data instead of a conglomerate of isolated findings, progress has been made in the evaluation of consultation.