Measurements of the 95Zr/ 238U equilibrium ratios in non-irradiated uranium salts gave the following results: (3·7 ± 0·8) × 10 −4 and (4·9 ± 1·0) × 10 −4 disintegrations per second of 95Zr per gramme of 238U in depleted and natural uranium, respectively. If it is assumed that the 95Zr activity in depleted uranium is produced solely by spontaneous fission of 238U, and if Segre's value of 8·0 × 10 15 years for the spontaneous fission half-life of 238U is taken to be correct, the 238U spontaneous fission yield for 95Zr is calculated to be (5·3 ± 1·1) per cent. Yields of 95Zr, 97Zr and 99Mo from 14·7 MeV neutron-induced fission of 238U were found to be 6·1 ± 0·6, 4·7 ± 0·5 and 5·7 ± 0·5 per cent, respectively.