This paper presents a study of the stratigraphy, sedimentation and structure of the Timiskaming Series [Precambrian] of the Kirkland Lake area, northeastern Ontario. It is suggested that this section be defined as the type section for the Timiskaming Series in Ontario. Interpretations of the geologic history of the epoch, the nature of the provenance area supplying sediments and the character and environment of deposition of the sediments are given. The sediments S. of the major Larder Lake break are tentatively correlated with the sediments in the belt to the N. of the break as Timiskaming in age, on the basis of detailed structural studies in Skead and Hearst townships. Evidence in Ontario and Quebec shows conclusively that the Keewatin and Timiskaming series of the Kirkland-Larder-Noranda area are separated by a major structural unconformity. Examination of the Timiskaming rocks discloses that the provenance area was composed of basic volcanics an intrusives, rhyolites and acid porphyries of great variety, minor amounts of chert, Fe formation, jasper and slaty graywackes, and rare syenite, granite and gneiss. Disintegration of the rocks of the area was largely mechanical. The Timiskaming sedimentation represents a distinctive magnafacies of eugeosynclinal environment.