Abstract. Kelly C, Mitrasetia T, Sugardjito J. 2017. An assessment of a tropical urban stream using benthic macroinvertebrates as a bio-indicator in Muara Angke, Jakarta,. A preliminary study was conducted on the populations, density and distributions of benthic macroinvertebrate species along the course of the Ciliwung/Angke River, Jakarta. The selected river section is highly urbanized and heavily polluted, and five study sites were selected along its course to assess the health of the river ecosystem. Benthic macroinvertebrates are used as a bio-indicator for evaluation of ecosystem health. Their different pollution sensitivities, wide distribution and relatively sedentary lives make them useful candidates for this role. The focal point of the study is the MuaraAngke mangrove forest and wetland, a small remnant wetland at the mouth of the river in Jakarta Metropolitan. A comparison is drawn between the different study sites to assess the health and potential utility of this unique habitat. Despite several intense pressures resulting from the highly urbanized surroundings, and the mangrove's position at the mouth of the river where pollution accumulation would be highest, the data collected from this site showed a macroinvertebrate population dominated by pollution -sensitive taxa, suggesting the mangrove itself continues to provide significant ecosystem services in water -purification.