We report here that certain drugs can protect Syrian baby hamster kidney cells (BHK) and 0.5 MiCi/ml for the desired time interval. Then they were rinsed with 2 ml of phosphate-buffered saline, and left for 1--8 hr with 1 ml of 5% trichloroacetic acid. The cells were dissolved in 0.8 ml of 2% Na2CO3 in 0.1 M NaOH. A 0.6 ml aliquot of this solution was added to 10 ml of Triton X-100-toluene-Spectrofluor scintillator and neutralized with 0.2 ml of 50% trichloroacetic acid. The radioactivity of samples was measured in an Intertechnique scintillation counter.