Samples of anorthosite from Stillwater Complex units AN-1 and AN-II (terminology of McCallum et al (1980)) were analyzed by instrumental neutron acitvation analysis (INAA) for FeO, CaO, Na2O, REE, and other trace elements. No compositional trend with stratigraphic position was observed. Mean concentrations for most elements are about the same for the three traverses (two for AN-II) for CaO, FeO, and Sr concentrations are slightly different for the three traverses. The elements are not normally or lognormally distributed among samples from a single traverse. Strong interelement correlations can be understood in terms of sample mineralogy. Little evidence for compositional evolution of minerals during precipitation of the entire Middle Banded Zone is apparent. As in lunar anorthosites, the component of trapped residual liquid is relatively insignificant (less than 5%). In addition to plagioclase, which makes up, on average, 90% of the anorthosites, the rocks contain interstitial pyroxene (augite and inverted pigeonite) and, in some cases, quartz, titano-magnetite, sulfides, and rare apatite and allanite. There is an inverse relationship between the amounts of pyroxene and quartz. General compositional trends, exemplified by La-Sc systematics, indicate that the bulk of the poikilitic pyroxene appears to be cumulus-adcumulus, presumably formed at the crystallization front from a magma saturated in plagioclase and pyroxene. A small fraction of the pyroxene and plagioclase plus all the quartz and other trace minerals formed from the minor trapped liquid component. The irregular distribution of pyroxene oikocrysts indicates that interstitial melt migrated substantially prior to final consolidation of the rock.