Results from 15 test borings and 8 seismic-refraction surveys in the northeastern quarter of the Ware quadrangle, Massachusetts, provide information on the buried-bedrock topography, evidence of overdeepening of Winimusset Brook valley, information on the thickness and lithology of lacustrine deposits in glacial Lake Winimusset, and indicate a need for reinterpretation of the areal extent of the lake. Glacial Lake Winimusset, which occupied this bedrock valley during the last stages of deglaciation, was more extensive and accumulated thicker lacustrine deposits than previously postulated. Lacustrine silt and clay deposited in this lake are as much as 100 feet thick. The lake extended at least 1 mile north of the Town of Wheelwright. -from Authors