The neutron yields of a series of actinide–beryllium sources have been measured. Some of the sources were compared with primary neutron standards in a manganese sulphate bath. The experimental procedure is described in detail and corrections for the loss of neutrons from the bath are discussed. These measurements include a comparison of the Chalk River Ra-α-Be and the National Bureau of Standards Ra-γ-Be standard sources. The majority of the actinide–beryllium alloy sources were then compared with the standardized sources in simple boron trifluoride counter systems.