A　thorough　analysis　of　the　losses　due　to　thermal-gradient-induced　stresses　in　slab　lasers　is　presented　in　which　depolarization　losses　due　to　thermal-gradient-induced　stresses　are　calculated　properly　by　treating　the　changes　in　the　dielectric　impermeability　tensor.　In　previous　analyses　of　this　problem,　the　approach　in　which　the　index　of　retraction　is　treated　as　a　tensor　quantity　is　only　applicable　in　the　limit　of　very　small　changes.　Issues　of　how　to　correctly　write　the　reduced-suffix　forms　of　the　tensors　are　also　considered.　Our　formalism　is　then　applied　to　an　edge-pumped　Yb:YAG　slab　laser.　We　consider　straight-through　propagation　as　an　example　of　the　formalism　and　indicate　its　application　to　the　case　of　zigzag　propagation.