Using data gathered from 114 graduates of North Central College (Illinois) between 1961-66 who held teaching positions in public schools, the academic, personal, and teacher characteristics of women who began teaching after age 35 were investigated. Data analyses indicated that the mature women (mean age 40) exhibited more academic ability, better personal adjustment, and greater teaching ability than two groups of younger women teachers (mean age 22). Relative to a random sample of younger women teachers, mature teachers were characterized by higher cumulative and education course grade point averages (GPA), and higher American College Entrance Examination (ACE) scores. Relative to both a random group and a GPA-matched group of younger teachers, mature teachers achieved more favorable Minnesota Multiphasic Personality Inventory (MMPI) scores, were rated more favorably by college faculty and teaching supervisors, and were viewed as highly effective teachers by the principals employing them. However, many evaluations by teaching supervisors were negatively correlated with principals' ratings of mature teachers, indicating the need for a more accurate method for the assessment and prediction of teacher effectiveness. Further research should be conducted to determine whether these findings can be generalized. (A 16-item reference list is included.) (Author/SM)