In the light of the current global financial and economic crises, how would governments in sub-Saharan Africa (SSA) allocate their budgets across sectors in response to a binding debt-servicing constraint? Within a framework of publicexpenditure choice, the present paper estimates constraint-consistent debt-service ratios and employs them in a Seemingly Unrelated Regression involving a five-year panel for up to 35 African countries over 1975-94, a period preceding the Highly Indebted Poor Countries (HIPC) initiatives. While observed debt service is found to be a poor predictor of expenditure allocation, constraining debt servicing shifts spending away from the social sector, with similar impacts on education and health. The implied partial elasticity of the sector's expenditure share with respect to debt is estimated at 1.5, the highest responsiveness by far among all the explanatory variables considered, including external aid. Thus, if the social sector is to be protected, sufficient debt relief for SSA countries should be pursued.A.K. Fosu 22. The debt service ratio, expressed as a proportion of exports, is employed to reflect the usual concept that it is export earnings, rather than GDP, that define the foreign-exchange constraint. Note also that other specifications were experimented with, but the linear appeared to provide the best fit.23. By 'noise', it is meant that the debt-servicing ratio is a poor indicator of the debt burden.24. This is because, as is well known in the statistical literature, a larger standard deviation of an explanatory variable translates to a lower standard error of the associated estimated coefficient.25. Note, with inclusion of T, that the specification becomes a one-way temporal fixed-effects model.26. The time-period dummy variables are specified as (0, 1), however. The double-log specification follows others such as Dao (1995), Fosu (2008, Gbesemete and Gerdtham (1992), and Ouattara (2006). Results based on the linear and quadratic (with respect to PREDSR) specifications show similar importance of the debt-servicing variable and are available upon request; however, the log-log specification appears to provide the best fit and additionally yields coefficients (elasticities) that are comparable across variables.27. The set of equations that include the social-sector expenditure variable, GESS, and the non-social sectors is estimated, and then the set with the disaggregated social-sector variables, GEE and GEH, together with the non-social sectors is also estimated. Note that the estimates for the non-social sector expenditures are identical between the two sets of equations.28. Note that not all functional sectors are represented here. The expenditure shares add up to 88 per cent; there is a residual 'other' category that is excluded from the SUR estimation, as it should be in order to render the system estimable.