Simple nitric acid leaching and alkali fusion techniques for the determination of the total content of fallout239,240Pu in deep-sea sediment were compared. Leaching neither with boiling conc. HNO3 nor with boiling conc. HNO3+H2O2 was found to be sufficient. The sodium hydroxide fusion technique yielded reproducible analytical results and is proposed as an optimum dissolution method for quantitative determination of the total content of fallout239,240Pu in deep-sea sediment.