The aim of this study was to investigate correlations between the shape of mandibular incisor crowns and crowding. Study models of 50 untreated white subjects (25 men and 25 women) with varying degrees of crowding were studied. The lower incisors were sectioned and imaged at the contact point and midpoint levels, and the mesiodistal width was measured. Crowding was quantified by using both Little's irregularity index and anterior tooth size-arch length discrepancy. The ratio of the 2 mesiodistal widths was correlated with Little's irregularity index and anterior tooth size-arch length discrepancy. In the women, the ratio showed correlations of 0.52 (P =.008) and 0.55 (P =.005) for central and lateral incisors, respectively, with anterior tooth size-arch length discrepancy. No predictors of lower incisor crowding could be established from mandibular incisor crown shape in this study.