Data obtained from seven years of measurements of the total content (hereafter, content) of carbon monoxide (CO) near St. Petersburg (59.88° N, 29.83° E, 20 m above sea level) are analyzed. Random errors of a single measurement and of daily means of CO content are about 5% and 1-4%, respectively. Comparisons of the measurement results for St. Petersburg, Ny Ålesund, and Zvenigorod have shown that the mean CO contents at the first two stations agree within 1%; for Zvenigorod, similar values are systematically higher by 15%. The annual mean CO cycle in the area of St. Petersburg for the period 1995-2001 has an amplitude of about 24%. Maximum values of the CO content occur in February, and its minimum values are observed in July-August. Analysis of a CO measurement series has revealed a sharp CO increase over St. Petersburg in November-December 1998. Maximum values of the CO content substantially (by 25%) exceed the mean CO content typical of the February maximum. Estimates of the rates of CO increase for St. Petersburg have demonstrated that the CO content in 1995-1998 increased at a rate of ∼3.5% per year. The CO content began decreasing in 1998-1999. The rate of CO decrease in 1999-2001 was ∼3.8% per year.