Several methods of coincidence counting of I-129 are examined. Efficiency functions are estimated for these different methods and compared with the results of experiments leading to the indication of the most suitable conditions of measurements. It was also found that the γ-efficiency of the 4 πβ methane flow counter for photons near 32 keV was 0.024 ± 0.005. Finally some general remarks are made on the extrapolation technique as used for coincidence counting.