The successful utilization of 238Pu as a biomedical radioisotopic power source requires that the external radiation of 238Pu be understood quantitatively and kept to a minimum. To achieve these objectives 238Pu metal (80 at.% 238Pu) of high chemical purity has been prepared and characterized. An electrorefining process was developed to prepare the metal on a 1-cm3 scale. The neutron emission rate of three lots of electrorefined metal was 2446 (±30) n/sec per gram Pu. Correcting this measured rate for chemical impurities and fast fission gives a spontaneous fission rate of 2234 n/sec per gram Pu, or 2800 n/sec per gram of 238Pu. Neutron and gamma dose rates were also measured. Plutonium-238-gallium alloy, 238PuO2, and 238PuN were prepared and evaluated as radioisotopic heat sources.