This paper describes the measurement of the absolute flux density at 408 MHz of five moderately strong radio sources by a method which has good sensitivity and negligible confusion problems. The flux densities of a further 37 sources are determined by relative measurement. The 42 sources are used to define an absolute flux density scale for the southern hemisphere. Comparison with absolute scales established in the north, using common sources, reveals a difference of approximately 10 per cent; flux densities given by the present scale being the higher.