The properties of the bottom waters (>100 m) of the Gulf of Maine are described using hydrographic data from 26 surveys between May 1978 and December 1983. The average temperature and salinity of the bottom water are presented from the different surveys for four regions of the Gulf—Wilkinson, Jordan, and Georges Basins and the Northeast Channel. The spatial variability across the Gulf was larger than the temporal variability in any region. The bottom water originates from Slope Water that enters the Gulf through the Northeast Channel. It is modified within the Gulf by vertical mixing with the near-surface waters of Scotian Shelf origin. A box model for the property changes during the summer-fall period indicates that the advection and mixing processes are of approximately equal importance in determining the bottom water properties. A winter convective input to the bottom layers is shown to occur only from the coastal areas around Wilkinson Basin in years when the surface salinity there was relatively high (>33.0‰). Advection and mixing rates calculated by the box model are in agreement with direct measurements of the inflow to the Gulf (Ramp et al., 1985) and mixing estimates from a budget for the intermediate layer waters in the Gulf (Hopkins and Garfield, 1979).