A combination of alpha-spectrometry, liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) was used for the determination of plutonium isotopes. 238Pu and 239+240Pu were measured by alpha-spectrometry after separation of Pu by anion-exchange using 236Pu tracer as recovery monitor. After alpha-measurement, one part of the sample was dissolved for determining 241Pu by LSC. Another part was used for the measurement of the 240Pu/239Pu atom ratio by AMS at VERA. Thus, it was possible to obtain complete information on the Pu isotopic composition of the samples. This method was applied to environmental reference samples and samples contaminated from nuclear reprocessing.