Gas cylinders made from composite materials receive growing popularity in applications where light weight is advantageous. Current standards base safety determination mainly on the demonstration of minimum amounts of endured load cycles and minimum burst pressure of a small number of specimens. This paper investigates the possibilities of a probabilistic strength assessment for safety improvements and cost and weight savings. The probabilistic assessment is based on destructive testing of small samples. The influence of sample size on uncertainty of the assessment is analysed. Also methods for assessment of ageing in service (degradation) are discussed and displayed in performance charts.