Nocturnal intragastric feeding of patients with certain hepatic forms of glycogen storage disease has been advocated as an effective treatment, resulting in improved blood chemical values and linear growth. We are reporting the long-term follow-up of five patients with glycogen storage diseases; three with type Ia, one with type Ib, and one with type III disease. All had improvement in one or more of the following: linear growth, serum glutamic oxaloacetate transaminase, total lipids, cholesterol, phospholipids, or triglycerides. None had significant improvement in venous CO2, serum lactate or urate. One of the patients in this study died after 1.1 years of treatment, and another patient developed hepatocellular carcinoma after 4.4 years of treatment. Nocturnal intragastric feeding, in conjunction with appropriate daytime feeding, is helpful in the management of patients with glycogen storage disease but response to treatment is variable, and it remains to be determined whether the ultimate prognosis of the diseases can be improved.