Procedures for regenerating visual pigment and restoring phototransduction have been established with freshly isolated, bleached rat retinas. Phosphatidyl choline liposomes containing a 500 microM mixture of retinal isomers, including the 9-cis and 11-cis forms, were employed and the results compared with dark-adapted retinas, incubated similarly but without retinal. The following were recovered in a 60 min incubation, rhodopsin (plus isorhodopsin) to 91% of the original rhodopsin concentration, 87% of cGMP and 89% of PIII amplitude at saturation. PIII amplitude vs. log intensity curves gave values of n between 0.6 and 1/2.0 and sigma between 85 and 439 quanta/micron 2. Human retinas, ranging from 18 to 58 hours postmortem and treated as above, also produced photoresponses. Of the 7 retinas studied so far, rhodopsin has been regenerated to 0.1-0.35 nmol/mg protein, cGMP to 23.5-49.2 pmol/mg protein, and PIII to 20-50 microV: in some cases a b-wave was also seen. Values of n varied between 0.6 and 1.0, and sigma between 132 and 3700 quanta/micron 2. PIII responses were also seen after retinas, approximately 30 hours postmortem, were incubated for a further 24 hours in fortified medium. After incubation, retinal vacuolation was reduced.