Trypanosomes compartmentalise the first 9 enzymes of glycolysis and glycerol metabolism in peroxisome-like microbodies known as glycosomes. The identity of the sequences that direct proteins into the glycosome has until now been uncertain. We show here that the peroxisomal tripeptide entry signal is sufficient to cause association of a bacterial enzyme with the glycosomes of Trypanosoma brucei. However, it works less efficiently than the C-terminal 21 amino acids of trypanosome glycosomal phosphoglycerate kinase.