Mid-level health managers in a developing country were studied to examine the extent to which they are able to use and analyse data they receive from a new health information system. Among 168 managers filling out a self-administered questionnaire, 52% could compute a simple cost-effectiveness ratio and 27% were able to calculate proportions. Only 43% of the managers were able to construct a cumulative graph similar to the one recommended by WHO. Facility with these tasks was not related to levels of training or age. Twelve out of 25 programme managers interviewed in depth did not know how well their particular programme had performed in the previous year. Similarly, only six of these managers knew their best and poorest performing districts. The results of this study suggest; 1) Training managers in data analysis and use is critical if health information systems are to actually improve health care delivery. 2) Data intended for the use of programme managers need to be presented in simple ways. 3) Further social research is required to understand how managers perceive and use data. 4) Efforts to ensure the use of data should not be seen as something to be 'added on' after information systems are in place.
