A VIDEOTAPED MOCK TRIAL WAS SHOWN TO EIGHT 6-MEMBER JURIES AND TO AN EQUAL NUMBER OF 12-MEMBER JURIES. THE MOCK TRIAL INVOLVED AN ACTUAL AUTOMOBILE NEGLIGENCE CASE THAT HAD BEEN SETTLED OUT OF COURT. IT WAS CONDUCTED ACCORDING TO PROCEDURES EMPLOYED IN MICHIGAN TRIAL COURTS. SUBJECTS WERE 144 STUDENT JURORS RANDOMLY ASSIGNED FROM UNDERGRADUATE SPEECH CLASSES AT THE UNIVERSITY OF MICHIGAN. AFTER VIEWING THE TRIAL, THEY WERE ADMINISTERED A PRELIMINARY QUESTIONNAIRE TO ASCERTAIN THEIR IMMEDIATE INDIVIDUAL VERDICT. A SECOND INDIVIDUAL QUESTIONNAIRE WAS ADMINISTERED TO COMPARE PREDELIBERATION AND POSTDELIBERATION OPINIONS AFTER LABORATORY SESSIONS WITH THE JURORS RESULTED IN A GROUP DECISION. THE PROBLEM OF SUBJECT MOTIVATION WAS RESOLVED BY GIVING STUDENTS THE IMPRESSION THAT THEY WERE VIEWING A REAL TRIAL AND BY INDICATING THAT THE RESULTS OF THEIR DELIBERATIONS WERE CRITICAL TO THE STUDY. ON THE BASIS OF STATISTICAL COMPARISONS, THE STUDY FOUND THAT THERE WERE NO SIGNIFICANT DIFFERENCES BETWEEN VERDICTS, LENGTH OF DELIBERATION, AND NUMBERS OF ISSUES DISCUSSED OF THE 6-MEMBER AND 12-MEMBER JURIES. JURORS OF SIX-MEMBER JURIES PARTICIPATED MORE IN DELIBERATION THEN DID THOSE ON 12-MEMBER JURIES; AND 6-MEMBER JURIES WERE NOT SIGNIFICANTLY MORE SATISFIED WITH THE DELIBERATIVE PROCESS THAN 12-MEMBER JURIES. WHILE NOT SIGNIFICANT, THERE WAS A TENDENCY FOR 6-MEMBER MINORITY JURORS TO PARTICIPATE MORE THAN 12-MEMBER MINORITY JURORS. FROM A SMALL GROUP COMMUNICATION STANDPOINT, THE SIX-MEMBER JURY MAY BE SUPERIOR TO THE LARGER GROUP SINCE THE SMALLER SIZE MAY ENCOURAGE MORE OVERALL JUROR PARTICIPATION. BECAUSE ONLY A SMALL NUMBER OF STUDENT JURIES WERE ANALYZED IN THE STUDY, HOWEVER, THE CONCLUSIONS CANNOT BE APPLIED GENERALLY. THE USE OF ONLY ONE CASE AT A TRIAL ALSO LIMITS THE ABILITY TO GENERALIZE THE FINDINGS. SUPPORTING DATA ARE TABULATED, AND THE QUESTIONNAIRES ARE NOT INCLUDED. (DEP)