This update of the experience at the University of California at Irvine with laser photoradiation therapy (PRT) encompasses the period between May 1981 and June 1983. The results of treatment of 77 patients are reported (head and neck, 39; breast, 33; and lung 5). Head and neck cancer patients received treatment to 114 sites with a complete response (CR) in 28, partial response (PR) in 42, stable disease (SD) in three, and no response (NR) in 34, and an undetermined response in seven. Breast cancer patients were treated in 395 sites with CR in 222, PR in 74, SD in one, NR in 92, and undetermined response in six. The lung cancer patients in this series responded poorly, if at all. In addition to the above patient trials, we have investigated the interaction of laser hematoporphyrin derivative (HPD)-PRT with a chemotherapeutic agent, Cisplatin, against an experimental tumor (RIF-1) in an animal model. We have been unable to demonstrate an additive effect of laser HPD-PRT at total light doses of 25 J/cm2 and 75 J/cm2 with Cisplatin at a dose of 7 mg/kg. However, no additional toxicity was observed in combination therapy, suggesting that sequential application of laser HPD-PRT and Cisplatin may be safely employed in clinical situations. Another area of investigation has been the evaluation of the light-scattering characteristics of a lipid emulsion designed for laser HPD-PRT of bladder tumors. We have demonstrated that it is feasible to gain uniform illumination of the bladder surface with the use of this light-dispersing medium.(ABSTRACT TRUNCATED AT 250 WORDS)