The Lewisian complex at Stoer comprises a diverse assemblage of paragneisses together with several generations of acid to basic orthogneiss. All lithologies are early-Scourian in age and underwent granulite-facies metamorphism in the Badcallian (c. 2.7 Ga) event. Petrogenetic modelling coupled with geothermometry yields a P-T estimate for the peak of metamorphism of 920-990°C and >11 kb, as well as estimates of conditions encountered during Inverian (c. 2.6-2.3 Ga) and Laxfordian (<1.7 Ga) retrogression. Certain lithologies, especially those of supracrustal origin, show evidence of partial melting. It is suggested that anatexis, controlled by the internal buffering of metamorphic fluids, may have been an important process in the evolution of the complex.