Daily measutements of visibility on 09 LST have been made at a rural site in Chong-won, Chong-book since 1991 to find out a possible influence of emissions of anthropogenic pollutants and water vapout in urban and rural environments. Daily visibility data collected over four-year period were compared with the available visibility and air quality data obtainde from other stations. Detailed examinations of our data showed that the frequency of fog occurrence (visibility .leq. 1 km) at a rural site (KNUE) was at least three times higher (77 days per year) than the frequency of fog both in Chong-ju city (19 days) and at the Air Force Base(AFB) in the rural area. We interpret that the higher frequency of fog at KNUE was due to abundant water vapour in the Mieho River (upstream of the Keum River) area. In Chong-ju city, fog usually continued for a relatively long duration, while it dissipated simewhat faster in the rural environment due to higher solar radiation in the countryside area. The number of misty (.leg. 6 km) days (including foggy days) at KNUE were 235 days as compared with 135 days at the AFB and 67 days in Chong-ju city. In turn the number of days with low visibility (less than 6 km) at KNUE was about 64% per year. Since the moisture alone in a calm morning does not produce a visibility impairment, there must had abundant condensation nuclei including anthropogenic air pollutants. Air pollution was examined, for instance, average values of TSP for November and December 1993 were 115 and 116.mu.g/m$^{3}$, respectively. We conclude that the above mentioned environmental conditions with moisture are favourable for the formation of fog and mist in the rural sampling site at KNUE. Additionally, we found at least 10 days of acid fog at KNUE in September 1994 alone. Measured pH values in the acid for water were in the range of 4.36 .sim. 5.01 with the mean value of 4.51 Our observations suggested that strikingly acid fog do occur occasionally even in the rural environment.