Physics calculations have been performed for repeated plutonium recycling in tight pressurized water reactor lattices. These calculations made use of the transport theory code CASMO combined with a 70-group nuclear data library variant that was created recently. The calculational model, which performs well for normal thermal reactors, was tested against measured data for tight lattices from the Swiss reactor PROTEUS. The test results are reasonably good and the model was applied to tight lattice power reactors without any modification. Four reactor systems, three of which contain tight lattices with plutonium recycling, were treated. The fourth one represents recycling in a normal lattice. Calculated results are given for various parameters. Particularly important are the natural uranium savings in the tight lattice systems relative to net consumption in the normal lattice system. The values found are between 10 and 35% for an ∼50-yr operating time for each system. However, in some of the calculations, the void reactivity results are positive. For these cases, there may actually be positive values in reality—especially in the latter part of the time period studied— which would lead to restrictions and somewhat reduced savings.