Background: To assess the quality of child health services in primary health care (PHC) facilities in Calabar, south-east Nigeria. Design: Cross-sectional, descriptive design. Methods: Key informant interviews, structured observation, self-administered questionnaire and focus group discussion. Setting: Calabar, south-east Nigeria. Participants: All 10 PHC facilities in Calabar, 252 PHC workers serving in the facilities, and 76 mothers whose children received care in the facilities. Outcome measures: Adequacy of structure (equipment and personnel); process (diagnosis, training and knowledge, use of national case-management algorithm, and supervision), and output (clients' satisfaction). Main results: PHC facilities were adequately equipped to the extent of providing immunization services and management of diarrhoea but not for other aspects of care expected of a PHC centre, including management of acute respiratory infections (ARI), a common problem in children in the region. Supply of essential drugs was inadequate in all centres and facilities for emergency care were lacking. Many of the health care workers (68.3%) had adequate training in immunization, and their knowledge scores on immunization issues (62%) was higher than in other aspect of PHC. Use of the national case management algorithm was low among PHC workers. Results of the focus group discussions with mothers showed that a few perceived quality of care to be poor. The main concerns were long waiting time, lack of essential drugs, and attitude of the health workers. Conclusions: Inadequacy in the quality of child health services in PHC facilities is a product of failures in a range of quality measures - structural (lack of equipment and essential drugs), process failings (non-use of the national case management algorithm and lack of a protocol of systematic supervision of health workers). Efforts to improve the quality of child health services provided by PHC workers in the study setting and similar locales in less developed countries should focus not only on resource-intensive structural improvements, but also on cheap, cost-effective measures that address actual delivery of services (process), especially the proper use of national guidelines for case management, and meaningful supervision. © 2005 Blackwell Publishing Ltd.