An extension of previous work on the analysis of pulse‐height distributions obtained with gamma‐ray sources placed inside well‐type NaI(Tl) crystals is discussed. Two methods are given for the determination of the photopeak efficiency of these NaI spectrometers. It is shown that the summing property of the well‐type crystal can be used to obtain the source strength and to yield information on the decay scheme of gamma‐ray sources.The photofraction, photopeak efficiency, and resolution are given for a 5‐in. diameter by 3‐in. long NaI crystal with a 1‐in. diameter well.