[en] In general, radioactivity measurements for volume samples are performed by the γ-ray spectrometry method with germanium detectors. In the method, peak efficiency curves must be obtained for each kind of sample in advance. For the reason, usually, many standard volume sources have been made which have different shapes, densities, matrix compositions and so on. This paper describes about a simple method for determination of γ-ray efficiency curves by the combination of Monte Carlo simulations and a single-point calibration using a standard point source. This method enables us to determine the efficiency curves for various types of samples and detectors easily and precisely. (author)