GAS IS A MEANS OF EVALUATING PROGRAM EFFECTIVENESS ON THE BASIS OF THE EXTENT TO WHICH INDIVIDUALIZED CLIENT GOALS, ESTABLISHED AT INTAKE, HAVE BEEN ACHIEVED UPON TERMINATION FROM THE PROGRAM OR UPON FOLLOWUP. A REVIEW OF GAS LITERATURE PRODUCED 91 EMPIRICAL STUDIES, OF WHICH 41 MET MINIMAL CRITERIA OF COMPLETENESS AND QUALITY FOR INCLUSION IN THE CRITIQUE. LIMITATIONS, PROBLEMS, AND IMPLICATIONS ARE IDENTIFIED IN AN ANALYSIS OF THESE STUDIES, WHICH ENCOMPASSING PROCEDURAL CONSIDERATIONS (GOAL-SETTING PROCEDURES, DETERMINATION OF LEVEL OF GOAL ATTAINMENT AT FOLLOWUP, REALISTIC GOAL SELECTION, TRAINING OF PERSONNEL, THE IMPORTANCE OF RECORDING BASELINE LEVELS AT INTAKE, GAS AS A TREATMENT TECHNIQUE) AND METHODOLOGICAL CONSIDERATIONS (RELIABILITY AND VALIDITY). ILLUSTRATIVE DATA FROM SELECTED STUDIES ACCOMPANY THE NARRATIVE. IT IS CONCLUDED THAT THE POPULARITY OF GAS AS AN EVALUATIVE TECHNIQUE IS JUSTIFIED NEITHER BY THE QUALITY OF SUPPORTIVE RESEARCH NOR BY THE FINDING OF EVEN THE BEST STUDIES. SEVERAL PROCEDURAL PROBLEMS HAVE ARISEN AS THE BASIC ASSUMPTIONS AND REQUIREMENTS OF THE ORIGINAL GAS MODEL HAVE BEEN VIOLATED. THERE ARE SERIOUS METHODOLOGICAL QUESTIONS ABOUT THE RELIABILITY AND VALIDITY OF GAS AND ABOUT THE DESIGN OF SOME OF THE MORE FREQUENTLY QUOTED GAS RESEARCH. THERE IS CONFUSION ABOUT WHETHER THE VALIDITY OF GAS CAN BE ESTABLISHED AND ABOUT WHAT A GAS SCORE ACTUALLY MEASURES. DESPITE ITS SHORTCOMINGS IN EVALUATIVE APPLICATIONS, GAS APPEARS TO BE SERVING USEFUL EDUCATIONAL AND INTERVENTION FUNCTIONS IN MENTAL HEALTH SETTINGS. AN ANALYSIS OF POLITICAL, FUNDING, IDEOLOGICAL, AND PRAGMATIC ADMINISTRATIVE CONSIDERATIONS IN THE USE OF GAS AS AN ALTERNATIVE TECHNIQUE MIGHT BE IN ORDER. CAREFUL COMPLIANCE WITH THE ORIGINAL GAS MODEL IS IMPORTANT IF GAS IS TO BE USED IN PROGRAM EVALUATION. CHARTS, INCLUDING SUMMARIES OF RELIABILITY AND VALIDITY STUDIES, ARE PROVIDED, TOGETHER WITH A LIST OF REFERENCES.