Primary health care (PHC) nurses provide care at polyclinics in Soweto. Our study assessed nurse competence in the clinical detection of important respiratory signs in 337 consecutive paediatric patients with respiratory complaints. The patients were then independently re-examined by two paediatricians, one of whom was arbitrarily chosen as a 'standard doctor'. The standard doctor found 95 patients with important respiratory signs; nurses detected the same signs in 45 and the other doctor in 44 patients. Therefore nurses detected important signs as well as could be expected, considering the inter-observer variation between doctors. The nurses did, however, significantly overdiagnose one condition, follicular tonsillitis. Our results suggest that the Soweto paediatric PHC nurses detect clinical signs with as much accuracy as doctors. This study adds to the available evidence that adequately trained and supervised nurse practitioners can provide high-quality health care.