Different methods such as full spectrum DPM (FSDPM), dual isotope estimation and inclusion methods were studied for the activity quantification of ³H and ¹⁴C in dual beta labeled samples using liquid scintillation analyzer. A standardized Packard tritiated water was used as tritium source and ¹⁴C activity was standardized by CIEMAT/NIST method and compared with the results obtained by the above three methods. Minimum detectable activity was 2100dpm/l for ³H and 1200dpm/l for ¹⁴C with acounting time of 300min. The accuracy of the results obtained was found to be within ±10%for ³H: ¹⁴C activity ratios 1:1,1:2,2:1,6:1,9:1,13:1and18:1.