Surface waters samples between Japan and US for radiocarbon measurement have been collected since summer 2003 by cargo ship with the help of a shipping company. As a first step, to investigate regional Delta C-14 distribution in the North Pacific, the samples collected in the summer season of 2003-2006 were measured using an accelerator mass spectrometer (AMS) at the National Institute for Environmental Studies (NIES) in Japan. Although during 2003-2006, a distinct decreasing trend of Delta C-14 in the subtropical region of the North Pacific was not observed, the average values of Delta C-14 in the subtropical region (Kuroshio Current, North Pacific Current and California Current regions) for the 4 years were 72 +/- 12, 69 +/- 10 and 47 +/- 11 parts per thousand, respectively, and indicate that the long-term decreasing trend of Delta C-14 in the surface waters since the 1970's is still continuing. (C) 2009 Elsevier B.V. All rights reserved.