We present new results from the Mace Head coastal station illustrating that open ocean new particle production and growth events occur frequently during periods of high oceanic productivity over the N. E. Atlantic. For the first time, we report events during which a recently-formed nucleation mode (similar to 15 nm diameter) is detected and is observed to grow into an Aitken mode (similar to 50 nm diameter) over periods up to 48 hours. A growth rate of 0.8 nm hour-1 is estimated in a typical case study, pointing to a source region similar to 700 km off-shore. The duration of the growth also suggests the particle production events are occurring over large spatial scales. Analysis of seven years of data show occurrence of extended growth events (lasting at least 24 hours) from March to September, with a peak occurrence in May. The events suggest that secondary marine boundary layer aerosol formation contributes to the marine aerosol population. Citation: O'Dowd, C., C. Monahan, and M. Dall'Osto (2010), On the occurrence of open ocean particle production and growth events, Geophys. Res. Lett., 37, L19805, doi:10.1029/2010GL044679.