A number of studies have concluded that the Myers-Briggs Type Indicator (MBTI) measures four general dimensions of personality; however, their findings also suggest that the MBTI's scales could benefit from improvements in their measurement precision. The degree to which the addition of newly constructed items to the Form F item pool would improve the measurement precision of the four primary MBTI scales was assessed. Using item response theory (IRT) to quantify each scale's performance, findings indicate that the new items substantially increased the test information functions (TIFs) and decreased the standard errors of measurement (SEM), especially in the critical area around the type cutoff scores (e.g., SEMs for scales containing the original plus new items were approximately half the size produced by the original MBTI items). The potential benefits of this increased measurement precision were discussed with respect to a number of applied testing issues. / Master of Science