Abstract It is proposed that 55Co is one of the most promising cobalt isotopes for use in nuclear medicine. The reaction of 3He particles with manganese were investigated as a new production method of 55Co. Cross sections and thick target yields were measured in detail for 3He reactions on 55Mn in the energy range of 10–40 MeV in order to determine the optimum conditions for the production of 55Co. Within the energy range of 29.0–37.0, 23.0–40.0 MeV, the thick target yields were found to be 52, 103 μCi/μAh respectively. When the energy range of 29.0–37.0 MeV was chosen, 0.8% of 56Co, 57Co impurities were observed. Other promising reactions reported in the literature are also discussed.