The cyanobacteria Microcystis firma and Synechococcus PCC 7942 were used to test their ability for photoproduction of glucosylglycerol, sucrose, and ammonia. For this purpose, the substantial accumulation and liberation of glucosylglycerol and sucrose during osmotic shock, and ammonia during carbon limitation, were exploited. The three substances were photoproduced with rates of 3-9-mu-mol mg-1 Chlorophyll a h-1, which is inferior to reported rates of hydrogen photoproduction.