are unipotent radicals of two opposite Borel subgroups B = B(Φ, R) and B − = B − (Φ, R) containing T . It follows from the classical work of Hyman Bass and Michael Stein that for classical groups Gauss decomposition holds under weaker assumptions such as sr(R) = 1 or asr(R) = 1. Later the second author noticed that condition sr(R) = 1 is necessary for Gauss decomposition.Here, we show that a slight variation of Tavgen's rank reduction theorem implies that for the elementary group E(Φ, R) condition sr(R) = 1 is also sufficient for Gauss decomposition. In other words, E = HU U − U , where H = H(Φ, R) = T ∩ E. This surprising result shows that stronger conditions on the ground ring, such as being semi-local, asr(R) = 1, sr(R, Λ) = 1, etc., were only needed to guarantee that for simply connected groups G = E, rather than to verify the Gauss decomposition itself.