Measurements of relative humidity (RH) and temperature were made on the internal environment of packing cases containing kimono objects during their transport between the National Museum of Japanese History (NMJH) and the North Carolina Museum of Art (NCMA). A compact solidstate memory recorder was used for the measurements, and the recorder was packed in a corrugated paper box with the objects. A number of these boxes were placed inside an outer case, constructed from five-ply plywood, lined with a canvaslined aluminium sheet and fitted with cushions of polyurethane foam. Two kg/m³ of Nikkapellet was placed in the case as a humidity buffering material when the case was closed. It was observed that poor thermal insulation of the case resulted in significant fluctuations in temperature and RH inside the case, and a rise in temperature caused a rise in RH. The ratios of the RH changes to temperature changes during the flight were 0.5 on the way to the NCMA and 1.3 on the way back. The set of results indicates that the moisture content of the silk fibers of the kimono objects was kept at a constant level during the outward journey, and decreased by about 2per thousand during the return. The change in the moisture content is attributed to a decrease in the airtightness of the case which caused greater infiltration of the external air.