The authors took manual and dynamometric measurements of the power of the extensor hallucis longus (EHL) muscle in 100 patients with juvenile hallux valgus and 141 normal patients. Three degrees of valgus deformation were recognized: mild (15-25 degrees), moderate (26-35 degrees), and severe (> 35 degrees). Neither the manual nor the dynamometric measurements showed any difference in EHL power between the normal patients and those with mild valgus deformity. In the patients with moderate valgus deformity, the manual measurement usually showed the EHL force to be the same as that of the normal patients, while the dynamometric measurement gave a lower value. The patients with severe valgus deformation were shown to have a slight to moderate loss of power on manual measurement and a greater loss of power on dynamometric evaluation. Both methods of measurement are equally reliable. When the valgus deformation is mild to moderate, any loss of EHL power must be attributed to another cause; when the valgus deformation is severe, however, it by itself provokes a significant loss of EHL power. The Dandy maneuver is unreliable only in cases of severe hallux valgus.