The microscopic structure of bulk amorphous red P has been investigated by Raman scattering. It is concluded that the phosphorus tubes of pentagonal cross-section present in Hittorf's P and KP//1//5 are the structural units of the amorphous red P network. Intratube and intertube correlations are responsible for intermediate range order effects. The Raman data indicate that a continuous transition from the crystalline to the amorphous state takes place for P.