We examined the presence of tattoo lesions in 613 small cetaceans belonging to nine species and originating from the Southeast Pacific Ocean, the Southwest and Northeast Atlantic Ocean as well as from the North, Baltic and Mediterranean Seas. Most of the specimens had been caught in nets or were found stranded in the period 1988-2002. Thirty-five bottlenose dolphins from the Sado estuary, Portugal were photographed alive in 1994-1997. Tattoo lesions were detected in 68 of 196 Lagenorhynchus obscurus, 33 of 54 Delphinus capensis, five of 12 Tursiops truncatus, 57 of 95 Phocoena spinipinnis from Peru as well as in 17 of 35 T. truncatus from the Sado estuary, in two of 10 Stenella coeruleoalba and one of four T. truncatus from the Mediterranean Sea. Prevalence of the disease varied significantly between species in mature specimens but not among immatures. It also varied very significantly between inshore (P. spinipinnis and Sado T. truncatus) and offshore or offshore-neritic (S. coeruleoalba, L. obscurus, D. capensis and Peruvian T. truncatus) odontocetes, being higher in adult specimens of inshore (53.5%) than of offshore (29.7%) taxa. This variation may be caused by immunotoxic environmental pollutants of continental origin like organochlorines. The coastal waters of Peru and the Sado estuary suffer from eutrophication and pollution from various origins. Direct correlation with pollutant loads needs to be investigated.