Recent implementations of Gbs−1integrated circuits are mentioned and used as the basis for a capability projection of the more promising technologies. After first describing the projection strategy, both the silicon and GaAs circuit families are assessed with regard to their performance limits. A shorter analysis of Josephson technology follows. For scaled down devices in silicon as well as several GaAs technologies, potential l.s.i. solutions with 2–3 GHz clock frequencies are prognosticated. The 3–6 GHz range should eventually be accessible to m.s.i. d.m.e.s.f.e.t. circuits, whereas GaAs s.d.f.l., j.f.e.t. and e.m.e.s.f.e.t. approaches promise v.l.s.i. complexity between 1 and 3 GHz. The range around 10 GHz appears to be solely a future domain of Josephson circuits (up to v.l.s.i).