THE STUDY INVOLVED EXAMINATION OF APPEARANCE RATES AFTER 279 WITNESSES WERE SYSTEMATICALLY ASSIGNED TO EXPERIMENTAL TREATMENT OR CONTROL NONTREATMENT GROUPS. THE METHOD OF ASSIGNMENT USED PUBLIC DEFENDER DAY IN PEORIA COUNTY, ILL., AS AN OPPORTUNITY TO ASSIGN ABOUT 50 PERCENT OF THE CASES TO THE EXPERIMENTAL GROUP. SUBJECTS IN THE EXPERIMENTAL GROUP RECEIVED ALL WITNESS INFORMATION SERVICES, INCLUDING A LETTER OF INTRODUCTION AND EXPLANATION OF WITNESS INFORMATION SERVICE, A REMINDER CALL 1 OR 2 DAYS BEFORE THE SCHEDULED COURT APPEARANCE, AND THE PROVISION OF A WITNESS AIDE IN THE COURTROOM. CONTROL GROUP WITNESSES WERE NOT MADE AWARE OF ANY OF THE WITNESS SERVICES. DESCRIPTIVE DATA WERE COLLECTED ON EACH WITNESS AND COURT CASE TO ELIMINATE OBVIOUS POTENTIAL CONFOUNDS. ONE CONFOUND, THE TIME BETWEEN INCIDENT AND COURT DISPOSITION, WAS DETERMINED TO BE SIGNIFICANTLY DIFFERENT BEYOND THE .05 LEVEL. TO CONTROL FOR THIS CONFOUND, A SECOND PHASE OF ANALYSIS WAS DESIGNED THAT DID NOT RESULT IN COMPARABLE DATA. ATTEMPTS TO CONTROL FOR THE TIME CONFOUND INDICATED THAT DESPITE TIME, WITNESSES WHO RECEIVED BASIC SERVICES APPEARED AT A HIGHER RATE. THE SECOND PHASE SHOWED AN OVERALL APPEARANCE PERCENTAGE SLIGHTLY HIGHER THAN THE EXPERIMENTAL GROUP IN THE INITIAL PHASE. TABULAR AND GRAPHIC DATA ARE PROVIDED. (RCB)