Nuclear medicine imaging techniques can help in patient evaluation where infectious and non-infectious inflammatory disorders are suspected. When selected and tailored to the clinical situation, most techniques already in use or available soon provide information with high sensitivity. However, almost all currently available techniques lack the specificity to discriminate between infectious and non-infectious inflammation. In undiagnosed fever, this non-specificity may be an advantage since fever of unknown origin is caused by infection in only about 25% of cases, but in the postoperative patient the reliable differentiation between infection and sterile inflammation is highly relevant to clinical management. The range of radiopharmceuticals to investigate infectious and non-microbial inflammatory disorders is expanding and developments in protein/peptide chemistry and in labelling technology should lead to agents with very high specific activities. Nuclear medicine has to add specificity to its already high sensitivity if it is to distinguish both categories of inflammatory disorder.