Prominent activity of the 1998 Giacobinid meteor shower was observed from 11h UT through 15h UT on October 8 in Japan. We carried out a high-sensitivity HD-TV observation of this activity at the Dodaira station, and detected 341 Giacobinid meteors, along with 127 sporadic meteors. The peak activity was around 13h05m UT with an peak influx rate of meteoroids of 1.6¿10-5 km-2 s-1 (magnitude ≤+7). The peak corresponded to solar longitude 195.071¿ (equinox J2000.0), which is different from the expected maximum of the Giacobinids at the solar longitude 195.4¿ (equinox J2000.0). The duration of the peak activity is shorter than that of the previous outburst in 1985. The apparent brightness ratio of the faint meteors during our observation is about 2.1, which is a rather small value compared to previous displays. ¿ 1999 American Geophysical Union