There is disagreement in the literature about the most common fracture type at the base of the proximal phalanx of the thumb in children below the age of adolescence. In this prospective study, 58 consecutive children aged 10 years or less with isolated fractures of the base of the proximal phalanx of the thumb were included and their radiographs were reviewed. The study included 38 boys and 20 girls with a mean age of 8 (range 1-10) years. After excluding one patient, in whom the type of fracture could not be determined, the most common fracture in the remaining 57 cases was the Salter-Harris type II fracture (72%), followed by the juxta-epiphyseal type II fracture (18%).