Membrane permeability coefficients (P0) of rabbit lung cells consisting primarily of alveolar epithelial and endothelial cells and of alveolar macrophages from dog lungs were determined for tritiated water, n-[14C]alcohols, and [14C]antipyrine over the temperature range 10 to 37 degrees C with the series-parallel pathway model. In the mixed cell preparation both the diffusional permeability to water (755 X 10(-5) cm.s-1 at 37 degrees C) and the response to temperature change (apparent activation energy, Ea, 10 kcal.mol-1) are greater than the corresponding values in the macrophages (110 X 10(-5) cm.s-1 and 4.8 kcal.mol-1, respectively). The permeability coefficients for the small alcohols (C1-C3) are similar and considerably higher than for water in both cellular preparations. The values of the permeability coefficients and the temperature dependence for antipyrine and the larger alcohols in the mixed lung cells differ from the values obtained in the macrophages. Comparison of our results with those obtained in erythrocytes and Novikoff hepatoma cells demonstrates the differences in water permeability in each cell preparation and the similarity in permeation for the more lipophilic solutes in the cell preparations. These differences may be important in the comparison of results obtained in isolated cellular systems and in intact tissues and organs.