  I discuss the problem of proton decay, from dimension four, five and six
operators, in superstring derived standard--like models. I classify the sectors
that produce color triplet superfields which may generate proton decay from
dimension five and six operators. I show that for two of these sectors there
exist a unique superstring doublet--triplet splitting mechanism that projects
out the color triplets by means of the GSO projection, while leaving the
electroweak doublets in the physical spectrum. I investigate possible proton
decay due to additional color triplets in the massless spectrum and due to
nonrenormalizable terms. I show that there exist models in which the dimension
four, five and six operators, that lead to proton decay, are forbidden by the
symmetries of the string models, to all orders of nonrenormalizable terms.
