[en] In this manual, the procedure to analyze radioactive zirconium is prescribed, which is contained in drain water from atomic energy plants. Samples are collected from sea water near the plants, marine organisms, and sediment of sea bottom. Radioactive niobium behaves together with radioactive zirconium, therefore the measurement is made for zirconium-95 and niobium-95 mixture. The method of analysis in this manual is the co-precipitation with lanthanum and the radiochemical analysis with a low background G-M counting system. The detectable levels are 1 pCi/l for sea water, 10 pCi/kg for marine living things, and 1000 pCi/kg for dried sediment of sea bottom. This manual also described on the method of collection of samples in detail. (Kato, T.)