Photoreduction of cytochrome c (cyt.c) in the presence of a bilayer membrane of amphiphiles having an N-ethylcarbazolyl (ECz) group was investigated. It was found that efficient energy migration among ECz groups promoted electron transfer to cyt.c, and the photoreduction yield was thus insensitive to the: concentration of cyt.c, but was determined mainly by the amount of a sacrificial donor bound to the membrane.