The specific features of combustion-wave propagation in a narrow tube have been studied experimentally in low-velocity regime for propane-air and hydrogen-air mixtures. For propane mixtures, an increase in the curvature of a flame surface correlates with the displacement of the laminar burning velocity maximum to the region of enriched mixtures. The combustion of lean hydrogen-air mixtures is accompanied by acoustic oscillations, which lead to a narrowing of the range of flame existence on combustible-gas flow rate. The rich hydro.-en-air flames propagate steadily.