In this study we have analysed the influence of temperature and time of storage and of repeated freezing on procalcitonin plasma concentrations ex vivo. We have also analysed the difference of procalcitonin concentrations in arterial or venous blood samples and the influence of different anticoagulation techniques on procalcitonin concentrations (serum, EDTA-, lithium-heparin- or citrate plasma). At room temperature (25 °C) a loss of procalcitonin plasma concentrations of 6.4% ± 2.6% (mean, 2 standard error of the mean) after 3 hours (4.6% ± 5.2% at 4 °C) and 12.3% ± 3.1% after 24 hours occurred (6.3% ± 5.0% at 4°C, n = 17 each). Comparing the procalcitonin concentrations of blood samples with different anticoagulants (n = 24 each), there was only a significant difference between procalcitonin concentrations in heparinized plasma and serum (+ 7.6%, difference of the mean). There was no significant influence of the blood sampling technique (arterial or venous line) and of repeated freezing/thawing cycles (up to 3 times) on the procalcitonin concentrations measured. Although the difference of sampling and storage of the blood on procalcitonin concentrations is not significant, multiple factors may act synergistically on the result of procalcitonin measurement. To keep variations of ex vivo conditions as minimal as possible, a standardized technique of anticoagulation, time and temperature of storage is recommended, e. g. the use of EDTA-plasma and storage at room temperature, when samples are measured within 4 hours after blood drawing.