Examination of pollen content and geochemical analysis of marine core BAR94-25 taken from ∼100 km north-west of Sumatra in the Andaman Sea reveals a ∼100,000 year record of environmental change as well as the influence of the Toba super-eruption at ∼73,000 years ago on the ecosystems of northern Sumatra. The record also contains an older volcanic ash dated to ∼89,000 years ago, allowing a comparison of the effects of two eruptions on the local environments of the island. The immediate effects of the older eruption on the ecosystem of northern Sumatra were limited, though a gradual and substantial increase in pine forest likely followed the event in the longer term. The Toba super-eruption at ∼73,000 years ago, however, had an instantaneous and devastating effect on the pine forests of northern Sumatra. Evidence for impacts of this super-eruption at ∼73,000 years ago on regional climatic conditions remains inconclusive. Climatic changes inferred from the pollen record or estimated via pollen transfer functions date to a few thousand years after the eruption, or are clearly linked to long-term climatic trends initiated a few thousand years before.