Infections due to Ps. aeruginosa are a problem in the tropics as in other parts of the world. Over a four year period, 15 patients attending University College Hospital, Ibadan, were proved to have septicaemia due to this organism and 13 patients died rapidly as a direct result of the infection. The two patients who survived the acute episode had received immediate treatment with at least one antibiotic active against Ps. aeruginosa: a third patient, who received immediate appropriate antibiotic therapy, was already suffering from aplastic anaemia and died rapidly despite treatment. The remaining patients received inappropriate antibiotic therapy because pseudomonas infection was not suspected at the time the diagnosis of septicaemia was made. Patients most at risk appear to be the very young and those with pre-existing malignant or other conditions affecting the defence mechanisms of the body: it is suggested that routine initial management of such patients should include a blood culture, followed by immediate treatment with an antibiotic combination that includes at least one agent likely to be active against Ps. aeruginosa. The development of medical services can lead to the introduction of ophthalmic or other operations on tissues that are highly susceptible to infection before facilities are provided for the maintenance of a pathogen-free environment. Following an outbreak of eye infection after cataract extractions, carried out in an old and unsatisfactory theatre, wide-spread room contamination was demonstrated with the same strains of Ps. aeruginosa that had been responsible for the clinical infections. Chemical disinfection of the theatre floor failed to eliminate the organisms, although other experiments suggested that the drying effect of air-conditioning would be successful in this respect. The wisdom of introducing such operations before the provision of adequate facilities is seriously questioned.