The relationship between student personality traits and achievement with either mediated self-instruction or didactic large group instruction was investigated. Subjects were 159 female third-year nursing students at Loyola University of Chicago. Subjects received instruction on tracheostomy care and intravenous (I.V.) therapy through either a lecture or an autoinstructional filmstrip/cassette program. Personality traits were assessed using: (1) the Dogmatism Scale, measuring the openness of the individual's belief system; (2) the Internal-External Scale, measuring locus of control orientation; and (3) the Self-Esteem Inventory, covering peers, family, schools, and personality interests. The filmstrip program was superior to the lecture method for I.V. therapy instruction, and a significant relationship was found between performance on the I.V. therapy test and high scores on the Self-Esteem Inventory. A very weak relationship was found between the instructional method employed and student performance on the tracheostomy care lesson. Findings suggest that analysis of the interactions between personality traits and type of instruction can assist teachers in assigning students to an instructional treatment. (LMM)