The Copenhagen Laboratory, UniversityofFilm detection of compounds labeled with the weak beta-emitters 3H and I4C is demonstrated for electroimmunoprecipitated proteins in agarose gels by means of the water-soluble fluorophor sodium salicylate. The degree ofenhancement offilm detection of tritium and carbon-14 with 0.7 M sodium salicylate paralleled fluorography with diphenyloxazole on polyacrylamide gels. The method was optimized and the sensitivity, expressed as radioactivity per cm immunoprecipitate, was 0.9 nCi/cm (2000 dpm/cm) in 24 h for 3H and 0.4 nCi/cm (830 dpm/cm) in 18 h for I4C. The procedure was found superior to the commercially available enhancement solutions 'EnHance' and 'Amplify'. Salicylate fluorography on Kodak X-Omat L and AR-5 films was about 30 and 60 times more sensitive than Ultrofilm 3H. With 14C-labeled anti-antibodies rocket electroimmunoprecipitation corresponding to about 50-100 pg protein could be visualized in 7 days. Conclusively, the method is rapid (soaking and drying require about 30 min), sensitive, reproducible, cheap, and advantageous if the immunoplates are to be stained for protein after fluorography.