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The temporal variation of 14C concentrations in atmospheric CO2 samples collected every 10 days was measured in the Takao area of Kanazawa, Ishikawa prefecture, Japan (36.52°N, 136.64°E), from April 1991 to December 1995. The monthly mean levels of 14C concentration in the Takao area demonstrated 10–50‰ lower concentrations than the background levels only in the winter season. This decrease seemed to be caused by the local fossil fuel contribution by heating in the winter season in the Takao area, which is located in an urban region near the center of Kanazawa. It is noteworthy that a remarkable peak was observed from late April to mid-May each year from 1991 to 1995 in the variation of 14C concentrations in atmospheric CO2. This phenomenon is similar to that of the so-called “spring peak” observed in Japan for other radionuclides. [ABSTRACT FROM AUTHOR]