Longitudinal growth data from 31 patients with hepatic glycogen storage disease (type I (8 patients), type Ib (three patients), type III (13 patients), and type IX (phosphorylase kinase deficiency) (7 patients) ) have been reviewed. All patients were below the mean for height at presentation; the mean height standard deviation scores were -2.13 (type I), -2.0 (type Ib), -2.4 (type III), and -1.6 (type IX). Untreated, most patients with type I and Ib grew slowly with no catch up growth but three patients with mild disease grew normally. Most children with type III disease grew at a normal velocity throughout childhood. Puberty was delayed and final height normal. Some of the children with type III and all of those with type IX had catch up growth throughout childhood. Intensive treatment of patients with severe forms of type I and Ib disease resulted in catch up growth, but this was not complete if the treatment was started late.