THE PURPOSE OF THIS STUDY WAS TO EXAMINE THE EFFECTIVENESS OF ASSERTIVENESS TRAINING IN DEALING WITH JUVENILE FIRST OFFENDERS. THE SAMPLE INCLUDED 22 MALES AND 23 FEMALES DRAWN FROM THE JUVENILE FIRST OFFENDER PROGRAM IN LEA COUNTY, N. MEX. THE PARTICIPANTS WERE RANDOMLY ASSIGNED TO THE FOLLOWING FIVE GROUPS: (1) ASSERTIVENESS TRAINING; (2) CLIENT-CENTERED COUNSELING; (3) WAITING LIST; (4) PRETEST AND POSTTEST ONLY; AND (5) POSTTEST ONLY. SUBJECTS WERE PRETESTED AND POSTTESTED WITH THE RATHUS ASSERTIVENESS SCHEDULE (R.A.S.) AND THE PIERS-HARRIS CHILDREN'S SELF CONCEPT SCALE (C.S.C.S.). TWO NULL HYPOTHESES WERE STATED PROPOSING THAT NO SIGNIFICANT DIFFERENCES BETWEEN THE MEAN PRETEST AND POSTTEST SCORES ON THE R.A.S. AND C.S.C.S. WOULD APPEAR AMONG THE FIVE GROUPS. AN ANALYSIS OF VARIANCE (ANOVA) ONE-WAY DESIGN WAS APPLIED TO THE DATA. FURTHER ANALYSES WERE ACCOMPLISHED USING A POSTERIORI CONTRASTS. THE MAJOR CONCLUSIONS OF THE STUDY WERE AS FOLLOWS: (1) ASSERTIVENESS TRAINING IN ADOLESCENT GROUPS CAN BE EFFECTIVE IN DEALING WITH JUVENILE FIRST OFFENDERS; (2) CLIENT-CENTERED COUNSELING WAS EFFECTIVE ALONE OR IN COMBINATION WITH ASSERTIVENESS TRAINING; AND (3) FURTHER INVESTIGATION OF JUVENILE FIRST OFFENDERS IS WARRANTED. TABULAR DATA, A BIBLIOGRAPHY, AND APPENDIXES WITH SAMPLES OF THE SURVEY INSTRUMENTS ARE PROVIDED. (JCP)