Three children with acrodermatitis enteropathica (AE) were treated with oral zinc dipicolinate (zinc-PA). The daily dose of zinc required to prevent exacerbations, when administered as the dipicolinate complex, was one-third the minimum amount of zinc required as the sulfate salt. The concentration of picolinic acid in the plasma of asymptomatic children with AE was significantly less than that of normal children. However, oral treatment with PA alone was ineffective. The plasma of the three AE children contained a measurable quantity of kynurenine which was undetectable in plasma from normal children. Absorption of an oral zinc load was normal. The results support the hypothesis that the genetic defect in AE is in the tryptophan pathway, although the role of PA in zinc metabolism remains to be defined.