Research on sexual dimorphism in proximal hand phalanges contributes to the assessment of the biological profile of an individual from human skeletal remains. Furthermore, it provides fundamental information for studying the origins of manual dexterity. The anatomy of proximal hand phalanges has been widely described, and the occurrence of sexual dimorphism has been reported in studies concentrating on sex determination. However, there is limited research focusing on the level of sexual dimorphism. Therefore, the aim of this study is to examine the degree of sexual dimorphism in proximal hand phalanges. A total of 661 bones from 160 adult individuals (86 men and 74 women) of the Athens collection were studied. Seven measurements were taken involving the maximum length and diaphyseal and epiphyseal widths. Descriptive statistics, t-values and percentages of sexual dimorphism were estimated. The results of this study indicate that, in almost all dimensions measured, men have larger proximal hand phalanges than women. Proximal hand phalanges present a high degree of sexual dimorphism (reached 24.78%). The phalanges of the left side demonstrate a higher degree of sexual dimorphism. The proximal phalanges of the thumb proved to be the most sexually dimorphic bones in the material. The minimum sexual dimorphism observed was in the maximum lengths of phalanges, whereas the most sexually dimorphic measurement is the medio-lateral width at midshaft. Copyright © 2013 John Wiley & Sons, Ltd.