Each case study for examining visitors' perception is often based on the fragmented information obtained from a sampling investigation that has been conducted at a certain place and time. Moreover, this method cannot monitor the secular variation and trend in population; and, as a result, we cannot help limiting the interpretation of the results obtained from the investigation. However, until recently, the secular variation and trend within the population has not been examined using the method involving the collection of data from a certain place at a certain time. Furthermore, the subjects in the investigation technique that is applied to capture the secular or seasonal variation in the population have hardly been discussed. This study was conducted in order to examine the problem involved in the method for investigating visitors' perception in a protected area and to obtain the pointers for further improvement. In this research, the reproducibility and stability of the results of sampling were verified on the basis of the questionnaire from a mail-back survey. The survey was part of an annual investigation conducted in Shiretoko National Park, where the recreational conditions have been changed.
