Item response theory (IRT) methods were applied to items from the 80-item Psychological Inventory of Criminal Thinking Styles (PICTS; G. D. Walters, 1995) to determine how well they measure the latent trait of criminal thinking in a group of 2,872 male medium security prison inmates. Preliminary analyses revealed that the 64 PICTS thinking style items, 32 PICTS proactive criminal thinking items, and 24 PICTS reactive criminal thinking items were sufficiently unidimensional to meet the local independence requirements of IRT. The PICTS was fitted to a 2-parameter logistic-graded response IRT model, the results of which showed that the 8 items measuring denial of harm (Sentimentality) displayed weak discrimination (a less than 0.5), whereas most of the proactive and reactive items displayed moderate to good discrimination (a greater than 1.0). Information function analysis revealed that all 3 components of a hierarchical model of criminal thinking--PICTS total scale, PICTS proactive factor, and PICTS reactive factor--displayed greater precision at higher rather than lower levels of the trait dimension. The study findings indicate that items from the PICTS Sentimentality scale do a poor job of measuring general criminal thinking, whereas items from the other 7 PICTS thinking style scales provide their most precise estimates at the upper end of the trait dimension. (Contains 4 footnotes, 4 tables, and 3 figures.)