The discovery of plastids in apicomplexan parasites1,3 raised the possibility that these organelles might harbour plastid-specific metabolic activities that could be blocked by therapeutic agents. Ideally, these agents would inhibit the parasites without harming their vertebrate hosts. Roberts et al.4 have made the promising dicovery that Apicomplexa are sensitive to the herbicide glyphosate (better known by its trade names of RoundUp, Zero or Tumbleweed), which is an inhibitor of the enzyme 5-enopyruvyl shikimate 3-phosphate synthase. They suggested that production of aromatic amino acids by the pathway involving this enzyme, the shikimate pathway, might be an essential function of the apicomplexan plastid, but here we present evidence that this pathway actually operates in the cytosol of Apicomplexa.