Journal of Tanzania Association of Foresters, 2004, 10:14-25One of the major ways of mitigating carbon emissions is by emission avoidance or conserving existing carbon (C) pools on the land through slowing deforestation or improved forest harvesting practices. Field measures of tree dimensions and chemical soil analysis for organic carbon were used to quantify the carbon (C) storage potential of three tropical montane rain forest ecosystems; one on the slopes of Mount Kilimanjaro and two (Usambara and Uluguru) in the Eastern Arc Mountains of Tanzania. The above ground and root carbon of trees ranged from 295±8 to 5/7 ± /7 o:'. The tree carbon storage was lowest in the Kilimanjaro forest (295±8 (SD) t h"), and highest in the Usambara forest (5/7 ± /7 (SD) t s'. The C storage in the Ulugurus was 388± /0 (SD) t «'. The soil carbon storage (/423.7 t h") in Kilimanjaro was significantly higher than that in tree biomass. On the other hand the soil carbon (4/8 ± /00 and 295 ± 53 t h") in the Usambara and Uluguru respectively) was significantly lower than the biomass carbon in both forests in the Eastern A rc forests. The potential of these ecosystems to act as carbon sink and mitigate greenhouse gas emissions is evident. This capacity for carbon storage. population pressure and the extensiveness of these forests in the region makes their conservation of global significance for carbon emission mitigation.