In order to know the harmful and toxic phytoplankton species of the ships that arrive at the port Santa Marta, samplings were realized in 33 ships in ballast water during the months of january-september of 2006. Altogether 26 species were recorded, of which 23 are harmful and 3 are toxic. Likewise, is was determined that great part of these species comes from the American continent, followed by the European continent and other regions. The great majority of the species found in ballast waters for this study, has been present in the region of Santa Marta. Nevertheless, are some harmful species like Leptocylindrus cf. minimus, Chaetoceros concavicornis, Chaetoceros debilis, Odontella aurita and toxic like Prorocentrum cf. balticum, which are potentially being introduced to the region. The near places of origin can be contributing to the increase of the rates of survival of these species.