This paper reports on an econometric structure-performance model for a mixed-market developing economy, the East African state of Malawi. A simultaneous equation model which was cross-sectionally heteroskedastic and time-wise autoregressive was estimated by instrumental variables using published and some new unpublished data. A binary probit model was estimated using new primary source data. Scarce factors like working capital and imported raw materials were found to be significant determinants of price-cost margins. Further, for the firms in the survey, upward price flexibility was found to be significantly influenced by reported input scarcities.