Quantitative ion exchange and 4π counting techniques have been used to measure the yields of four nuclides not previously determined by mass spectrometric analysis. Values of 6.57, 6.30, 4.74, and 5.71% were obtained respectively for Ba139, La141, Sr89, and Sr91 relative to a value of 6.32% for the yield of Ba140. A precision better than 1.3% was achieved in the measurements.