Among 27 cases of Pseudomonas septicaemia in the Department of Paediatrics of Queen Mary Hospital from 1981 to 1988, we have identified 10 children without known predisposing causes before presentation and report their clinical features. Six were infants, of whom 4 developed shock on admission and died. Ecthyma gangrenosum was present in 4 patients. Pseudomonas aeruginosa was isolated in 8 patients. All isolates, except Ps. cepacia, were sensitive to gentamicin. One patient had cyclical neutropenia. Another had an appendicular abscess. Salmonella was cultured from the stool in one patient. Although Pseudomonas septicaemia is normally considered to be associated with underlying immunodeficiency, in 22% it occurred in previously healthy children. Mortality is high especially in infants who develop septicaemic shock. It is advisable to cover for Pseudomonas septicaemia with aminoglycosides or ceftazidime in sick septic infants.