Household use of solid fuels, such as dung, wood, agricultural residues, charcoal, and coal, is likely to be the largest indoor source of air pollution in developing countries. Combustion of solid fuels in inefficient stoves under poor ventilation conditions can result in large exposure burdens, particularly for women and young children, who spend the major part of their time at home. The importance of this public health and environmental issue is reflected in the inclusion of the percentage of households using solid fuels as an indicator towards the achievement of the Millennium Development Goal (MDG) for environmental sustainability. This article outlines the model used for completing missing country data for household use of solid fuels. Out of a total of 181 country data points reported, data were available for 94 countries. These included estimates from 42 countries where household solid fuel use was previously unknown, largely from the recently conducted World Health Survey. Based on the data available for these countries, using step-wise regression, a model to predict household solid fuel use based on rural population, gross national income (GNI) and geographic regional variables was developed. Thirty-five data points were estimated using this model. In general, household solid fuel use seems to be lower in 2003 than in 2000. Yet, even with increases in economic development and urbanization, drastic reductions in household solid fuel use are unlikely to occur in the absence of targeted programs to promote cleaner fuels.