Temperature effect of the photocyle of sensory rhodopsin (sR) was studied by nanosecond spectroscopy. Though the formation yield of sR(M) (sR(370)) was sharply decreased with temperature, those of sR(K) (sR(680)) and sR(L) were insensitive to temperature changes. These results show the existence of the branching process back to sR from sR(L). The absorption maxima for sR(K) and sR(L) were 595 +/- 5 and 555 +/- 15 nm, respectively.