1. The urinary excretion of acylglycines has been studied in four patients with propionic acidaemia.
2. Propionylglycine was found in each of the patients.
3. This compound has not previously been detected in human body fluids. Propionylglycine was not present in the urine of control subjects or patients with non-ketotic hyperglycinaemia.
4. The excretion of propionylglycine was greatest in patients receiving the least dietary control.