We strongly encouraged a long run of time-series photometry on XTE J1118+480 with our spectroscopic campaign. The latest X-ray transient XTE J1118+480 are showing a periodicity of about 0.17d, but from observations at only one site, aliases cannot been removed. In fact, 0.34d period is suggested on the basis of 0.3 day observation in IAUC 7407. I think it is a good time now to make clear its period through international photometric campaign. If you can get a time-series photometry in this few days, we strongly encouraged to observe XTE J1118+480. If you can do, please notice us the schedule or result. regards, Makoto Uemura and Taichi Kato