THE SAMPLE WAS COMPOSED OF 360 MALE AND FEMALE STUDENTS, RANDOMLY ASSIGNED TO 1 OF THE 2 JURY SIZES. JURORS WERE PRESENTED WITH TAPE-RECORDED TRIAL SIMULATIONS AND WRITTEN CASE SUMMARIES IN WHICH WEIGHTED FACTS SUGGESTED EITHER HIGH OR LOW APPARENT GUILT. A 6-MEMBER AND A 12-MEMBER JURY WERE PRESENTED WITH CASE MATERIALS SIMULTANEOUSLY AND THEN SEPARATED INTO ROOMS TO DELIBERATE THEIR VERDICT. JURIES WERE INSTRUCTED TO REACH UNANIMOUS VERDICTS. A HUNG JURY WAS DECLARED WHEN THE JURY FAILED TO REACH CONSENSUS AFTER THREE ATTEMPTS AND A TOTAL DELIBERATION TIME OF OVER 1 HOUR. PREDELIBERATION EQUIVALENCE OF JURORS AND GUILT MANIPULATION CHECKS INDICATED NO SIGNIFICANT DIFFERENCES IN JURY MAKE-UP, AND THAT THE MANIPULATION HAD BEEN EFFECTIVE. CHI SQUARE ANALYSIS INDICATED THAT THE HIGH APPARENT GUILT/6-MEMBER JURY CONDITION RESULTED IN A SUBSTANTIALLY HIGHER CONVICTION RATE THAN DID THE OTHER 3 EXPERIMENTAL CONDITIONS WHICH DID NOT SIGNIFICANTLY DIFFER FROM EACH OTHER. HUNG JURIES ACCOUNTED FOR 8 OF THE 16 NONGUILTY VERDICTS IN THE 12-MEMBER JURIES, WHILE NO HUNG JURIES OCCURRED IN THE 6-MEMBER JURIES. MEAN TIME OF DELIBERATION WAS LONGER FOR 12-MEMBER JURIES (32.10 MINUTES) THAN FOR 6-MEMBER JURIES (17.80 MINUTES). THE SHORTEST DELIBERATION TIMES WERE FOR THE HIGH APPARENT GUILT/6-MEMBER JURY CONDITION. IN RESPONSE TO A POSTDELIBERATION QUESTIONNAIRE, 6-MEMBER JURORS INDICATED THAT THEY FELT A LARGER JURY SIZE WOULD HAVE PROMOTED A MORE PRODUCTIVE DISCUSSION, WHILE 12-MEMBER JURORS INDICATED THAT THEY FELT A SMALLER JURY SIZE WOULD HAVE BEEN MORE PRODUCTIVE. SATISFACTION WITH PARTICIPATION IN DISCUSSION WAS GREATER IN THE 6-MEMBER THAN IN THE 12-MEMBER JURIES, AND 6-MEMBER JURIES WERE MORE LIKELY TO FEEL A JUST VERDICT HAD BEEN REACHED (ALTHOUGH THIS MAY BE ATTRIBUTABLE TO THE LARGE NUMBER OF HUNG JURIES IN THE 12-MEMBER CONDITION). DISCUSSION WAS FELT TO BE MORE THOROUGH IN 12-MEMBER JURIES THAN IN 6-MEMBER JURIES PARTICULARLY IN LOW APPARENT GUILT CONDITIONS. FINDINGS DO NOT SUPPORT THE SUPREME COURT CONTENTION THAT JURY SIZE IS NOT AN IMPORTANT FACTOR IN JURY VERDICTS. FINDINGS SHOW THAT THE MAJOR EFFECT OF JURY SIZE IS THE DECREASED TENDENCY FOR 6-MEMBER JURIES TO BE UNABLE TO REACH A VERDICT AND THAT THIS OPERATES TO THE DISADVANTAGE OF THE HIGH APPARENT GUILT DEFENDANT. IN GENERAL THESE RESULTS ARE CONSISTENT WITH THE EXPECTATION THAT THE VIABILITY OF A MINORITY POSITION IS A FUNCTION OF THE ABSOLUTE SIZE OF THE MINORITY, INDEPENDENT OF ITS PROPORTIONAL SIZE. REFERENCES AND NOTES ARE PROVIDED. (JAP)