The speed of sound in methane has been measured with an estimated uncertainty of 0.003 per cent in the temperature range 125 K to 250 K at pressures up to 1.4 MPa. The results are compared with the most recent equation of state for methane and the agreement is generally within 0.03 per cent except near to the vapour pressure where deviations of up to 0.1 per cent are found. Isobaric perfect-gas heat capacities and second and third acoustic virial coefficients have been determined from the results. These same quantities have also been obtained at temperatures in the range 275 K to 375 K from a re-analysis of earlier measurements of the speed of sound.