To gauge the quality of river in terms of biological health, an investigation on the distribution of macroinvertebrate along Sungai Asah, Pulau Tioman, Pahang, Malaysia at three main stations (downstream, midstream and upstream) was conducted. The river macroinvertebrates were represented by nine orders, 45 families and 329 individuals across the three sampling stations. The most commonly found family was Diptera contributing 99 individuals to the total macroinvertebrates, followed by Trichoptera (80 individuals) and the least found order was Haplotaxida with only two individuals. The pollution intolerant taxa Ephemeroptera was found at all the sampling stations. The biological monitoring working party (BMWP) score at midstream of the river indicated the area was not impacted by pollution, but the EPT index was Poor at 2.8. The low number Odonata aquatic macroinvertebrates in Sungai Asah indicates that Sungai Asah was disturbed and impacted by human recreational activities.
