Nucleation of new, ultra-fine, aerosol particles has been observed in the clean marine coastal atmosphere under a variety of conditions. These nucleation events were observed to occur frequently over spatial scales of 10's--100's of metres and temporal scales of seconds to minutes. Two conditions appeared to be necessary for nucleation event to occur: low tide and solar irradiation. The requirement of low tide conditions suggests that the exposed shore area provides the source of new particle precursors. It is speculated that VOC and/or alkyl halide derivatives contribute to nucleation under these conditions. Nucleation rates were calculated to be ≈103--104 cm-3 s-1, suggesting that the coastal zone is an important source of atmospheric nuclei. ¿ 1998 American Geophysical Union