Human melioidosis is endemic in South East Asia and tropical Australia. However, increasing numbers of case reports are coming from other parts of the world. Increasing world travel and the potential for person-to-person infection in non-endemic areas make the likelihood of physicians and medical microbiologists encountering the disease far greater than heretofore. Both the disease, melioidosis, and the causative organism,Pseudomonas pseudomallei, have unusual features which render them worthy of consideration. In this review, an overview is given of the microbiology ofPseudomonas pseudomallei. Original studies on the presence of fimbriae are presented and factors influencing pathogenicity of the organism discussed. Descriptions of the properties of the various ‘exotoxins’ are presented. Current veterinary and medical knowledge relating to the disease is outlined. Attention is drawn to those features—prolonged latency, multiplicity of presenting conditions and lack of a specific diagnostic characteristic—which make diagnosis difficult. Finally, details of an ELISA technique for the detection ofPseudomonas pseudomallei toxin are described. This may represent a method for rapid screening of patients allowing appropriate therapy to begin at the earliest moment.