Finite-size effects in stacks of phospholipid bilayers, in the fluid L alpha phase, are investigated using samples oriented on silicon substrates. Recently in this journal, such effects have been suggested as the probable cause of reduced lamellar repeat spacings in very thin samples made up of a few (<10) bilayers. Our systematic studies on samples of different thicknesses do not support this conclusion. At full hydration all samples are found to have the same repeat spacing, irrespective of their thickness. At lower hydrations, on the other hand, very thin samples, consisting of only a few bilayers, have a slightly larger spacing.