The time allowed for life testing to assess the reliability of a product is continuously reduced and the test at normal use conditions often yields few or no failures. This situation especially occurs in testing products with long lifetime such as pneumatic cylinders. Performance degradation data often provide more accurate estimates on product reliability than those from failure time data. This paper presents a method for estimating parameters of lifetime distribution using the performance degradation data of pneumatic cylinders at normal use conditions. For this purpose, degradation analysis was carried out and the estimates from performance degradation data were compared with those from failure time data. According to the results, when considering test time and an uncertainty of reliability estimates, degradation analysis was strongly recommended rather than failure time analysis with censored data for the pneumatic cylinder.