The evaluation of potential graduate students is difficult because of differing backgrounds of the students and the variability of grading scales used by different universities. A diagnostic examination has been given the last 7 yr to 69 entering soil science graduate students at Iowa State University to determine their entry-level skills. The examination contained 150 questions covering 12 basic categories of soil science. Students with a soil science background performed better than students without a soil science background, but there was no relationship between performance on the examination and country of origin, TOEFL score, degree sought, or undergraduate class quartile. Results of the examination were highly correlated with the grade received in a beginning graduate-level course (Soil-Plant Relationships) and with the student's cumulative graduate grade point average at Iowa State University.