From 1988 through 1992 we studied the overwintering number of brown-marmorated stink bugs (Halyomorpha mista), at Unazuki Spa Town in Toyama Prefecture, Japan, where the overwintering flight of Halyomorpha mista has been observed every year. The flight of H. mista to the wall surface of buildings starts usually at the end of September and reaches a peak around the 3rd week of October. The coming-fly of bugs ceases at the end of November. The flight of stink bugs started in the daytime when the maximum temperature reached nearly 25℃ after overnight minimum temperature of about 15℃; the maximum number of bugs was recorded on an autumn day after the minimum temperature fell below 10℃. Regarding the slit traps which were set on the building roofs, more bugs were attracted to the slit traps which faced riverside than to those which faced the mountains. The natural wood-color board (coated with clear lacquer) attracted more bugs than boards painted in black or white. The bugs attached to the slit traps were observed 1 or 2 weeks after the onset of their flying to the wall surface of buildings.