THE IDEA FOR THE BOOK GREW OUT OF A CONFERENCE HELD IN 1974 BY THE ALCOHOL, DRUG ABUSE, AND MENTAL HEALTH ADMINISTRATION. EVALUATION IS BECOMING A POPULAR SUBJECT TAUGHT IN GRADUATE PROGRAMS RELATING TO HUMAN SERVICES. IT IS NOT UNCOMMON FOR LOCAL, EVEN MINIMALLY FUNDED, SERVICE AGENCIES TO EXPEND A SIGNIFICANT PORTION OF THEIR SCARCE RESOURCES ON THE EMPLOYMENT OF AN EVALUATOR. EVALUATION RESEARCH IS THE ANALYSIS OF PROGRAM EFFECTIVENESS THROUGH THE USE OF SCIENTIFIC METHODS TO APPRAISE SUCCESS. IN PRINCIPLE, EVALUATION IS RELATIVELY SIMPLE AND EASILY UNDERSTOOD. A SERVICE OF SOME TYPE IS OFFERED BY AN AGENCY OR PRACTITIONER TO A PATIENT, CLIENT, OR COMMUNITY GROUP. A SET OF GOALS IS ESTABLISHED FOR THAT SERVICE, AND A METHOD IS DEVELOPED OR ADOPTED TO MEASURE ACCOMPLISHMENTS OF THE SERVICE TOWARD STATED GOALS. OUTCOME IS A CENTRAL ISSUE IN EVALUATION, ALTHOUGH IN MANY CASES THE FOCUS IS ON PROCESS. EVALUATION ALLOWS FOR THE COMPARISON OF SERVICES OF SIMILAR AGENCIES OR PRACTITIONERS IN ORDER TO MAKE CONSUMERS BETTER INFORMED AND ALSO ALLOWS FOR THE COMPARISON OF SERVICES IN RELATION TO COSTS. COST-BENEFIT OR COST-EFFECTIVENESS STUDIES ARE ESSENTIAL IN A SITUATION WHERE RESOURCES ARE LIMITED AND THE CONCERN IS TO DETERMINE WHAT WORK CAN BE DONE UNDER CONSTRAINTS. FROM THE PERSPECTIVE OF PERSONS INSIDE AN AGENCY, EVALUATION STUDIES PROVIDE BOTH THE IMPETUS AND THE INFORMATION TO FACILITATE PROGRAM IMPROVEMENT. FOUR DIFFICULTIES ASSOCIATED WITH EVALUATION ARE: (1) GOALS OF MOST AGENCIES OR PRACTITIONERS ARE NUMEROUS, SUBTLE, AND SOMETIMES IMPOSSIBLE TO SPECIFY; (2) THE CHOICE OF GOALS IS A DIFFICULT TASK AND THE PARTICULAR SET OF GOALS SELECTED DEPENDS PRIMARILY UPON WHO IS DESIGNATED TO CHOOSE GOALS; (3) ONCE COMPLETED, AN EVALUATION STUDY IS LIKELY TO PRODUCE A MASS OF STATISTICS THAT REQUIRE INTERPRETATION; AND (4) MOST EVALUATION STUDIES HAVE NEGATIVE RESULTS, I.E., THEY ARE UNABLE TO DEMONSTRATE THE EFFECTIVENESS OF A PROGRAM UNDER STUDY. EVALUATION IS USEFUL IN ASCERTAINING THE GENERAL UTILITY AND EFFECTIVENESS OF A CLASS OF PROGRAMS. BECAUSE EVALUATION STUDIES ARE EXPENSIVE, TIME CONSUMING, AND REQUIRE HIGHLY TRAINED PERSONNEL, IT IS UNREALISTIC TO EXPECT THAT EVERY PROGRAM OR SERVICE AGENCY WILL UNDERTAKE AN EVALUATION. NOTES ARE INCLUDED. (DEP)