Although the killing of giant tortoises in the Galapagos Islands has been prohibited since 1933, poaching of tortoises still occurs. Personnel of the Galapagos National Park Service and the Charles Darwin Research Station regularly survey populations of tortoises throughout the archipelago and report all dead tortoises found. For the 10-year period 1995–2004 the field personnel reported evidence of 190 giant tortoises killed, primarily on the southern portion of Isabela Island. For the first 6 years the number of tortoises found killed was <15 per year, but since 2001 the number killed has increased dramatically, with 49 tortoises poached in 2004. During the same 10 years the number of tortoises found dead from natural causes was 131. Many of these deaths can be attributed to events associated with the 1997–1998 El Niño or with outbreaks of disease on Santa Cruz Island in 1996 and 1999. The results indicate that poaching exceeds natural mortality, and is a significant factor affecting these long-lived and slow-reproducing animals. Environmental education efforts in the human population of southern Isabela appear to have had little effect. Because tortoise poaching takes place at a small number of sites, effective enforcement at those sites could reduce killing of tortoises.