Following parenteral antibiotic administration, various factors influence the persistence of residues at the injection site, for example, the antibiotic itself, the composition of the formulation, the degree of irritation induced and the species of animal medicated. Routine testing for the detection of such residues is lacking in the EEC and even the absence of residues in the urine is no guarantee of their absence at the injection site. International regulatory guidelines concerning the permitted residue levels and the permitted extent of irritation at the injection site have yet to be agreed upon. By establishing such limits, it is hoped that the presence of drug residues can be avoided and at the same time 'good veterinary practice' can be facilitated.