The effectiveness of using the Perry Scheme of Intellectual and Ethical Development (PSIED) was assessed with vocationally undecided students. Erwin's 1981 Scale of Intellectual Development (SID) was administered to 290 vocationally undecided college students (131 males and 156 females ranging aged 17 to 42 years with a mean age of 20.2 years) at a large midwestern university. The SID was administered to the students at the beginning and end of a 1-semester career planning course. Students also completed My Vocational Situation (MVS), the Career Development Inventory (CDI), and the IPAT Anxiety Scale (IPATAS). The responses to each instrument were cross-analyzed to identify correlations between the SID and the MVS, CDI, and IPATAS. Correlations were presented with respect to career planning, career exploration, decision making, world of work information, preferred occupation, career development attitudes and knowledge, and total career orientation. The various instruments were also cross-correlated in terms of dualism, relativism, commitment, empathy, and covert and overt anxiety. The study confirmed that the PSIED can assist career counselors in discovering diversity in vocationally undecided students. Specific conclusions were also drawn regarding the validity of selected scales of the individual measures. (MN)