Reanalysis of the data from the 1966 Great Lakes-Illinois River Basin Project (GLIRBP) of the Federal Water Pollution Control Administration (FWPCA) reveals some of the large-scale persistent summertime circulation patterns in Lake Huron. The greatest density of data from the original 45 current meter moorings covers June-August 1966, when some 21 stations returned synoptically significant data from current meters at depths of 10 and 15 m. From this somewhat sparse sample it is deduced that at 10-m depth a counterclockwise circulation dominates the northern two thirds of the lake. The shallower southern portion shows a more complex pattern, with generally southward flow along the shorelines on both sides and a return flow northward near the center line of the southern basin. This latter pattern may decay later in the summer, but the data become too patchy for definite analysis. The data set from 15-m depth indicates similar circulations. Spectral analysis of currents at individual stations reveals a strong inertial rotation of the current vector at open lake sites. Only the data from the Straits of Mackinae lack the inertial component and are dominated by the lunar semidiurnal tide and the seiches of Lake Michigan.