Eradication programmes were initiated against infestations of the introduced blackberry species R. adenotrichos and R. megaloccocus on Santa Cruz Island, Galapagos, Ecuador in 1999 and 2000 respectively. The species were judged to be likely invaders even though neither produced viable seeds in Galapagos. Prior to eradication in 2003 these infestations occupied an area of less than a quarter hectare. I estimate the time and dollar cost of eradication of R. adenotrichos and R. megaloccocus to be US$11,322 US dollars/1 738 hours. More than half of these costs were sustained in extensive systematic searches of 330 ha surrounding known infestations. Herbicide accounted for less than 1 % of total costs. Control was undertaken using the herbicides glyphosate, and a combination of metsulfuron methyl and picloram. I recommend using teams of workers dedicated to eradicating known or potentially invasive species early in the invasion process or prior to establishment in Galapagos.