A checklist based on net samples taken twice weekly from 2001 until May 2003 is presented. Identification is based on direct light microscopic observations and after taking some organisms in culture. The checklist includes 227 taxa observed at Helgoland Reede sampling station. 132 species of diatoms from 53 genera and 95 species of dinoflagellates from 35 genera have been recorded from net samples and cultures. 35 diatom and 28 dinoflagellate taxa were documented for the Helgoland phytoplankton for the first time. The list does not claim to be complete, but provides an updated list of the taxa found on Helgoland and, for convenience of the reader, also published data for different adjacent areas.