Global concern about deforestation caused by fuelwood shortages prompted the introduction of Prosopis juliflora to many tropical areas in the 1970s and 1980s. pjuliflora is a hardy nitrogen-fixing tree that is now recognised as one of the world’s most invasive alien species. The introduction and subsequent invasion of pjuliflora in the Lake Baringo area of Kenya has attracted national media attention and contradictory responses from responsible agencies. This paper presents an assessment of the livelihood effects, costs of control and local perceptions on pjuliflora of rural residents in the Lake Baringo area. Unlike some other parts of the world where it had been introduced, few of the potential benefits of pjuliflora have been captured and very few people realise the net benefits in places where the invasion is most advanced. Strong local support for eradication and replacement appears to be well justified. Sustainable utilisation will require considerable investment and institutional innovation.