  We study the simplest renormalizable scalar leptoquark models where the
standard model is augmented only by one additional scalar representation of
SU(3) x SU(2) x U(1). The requirement that there be no proton decay from
renormalizable interactions singles out two such models, one of which exhibits
an unusual top mass enhancement of the mu -> e gamma decay rate. We analyze the
phenomenology of the model with the unusual top mass enhancement of loop level
chirality changing charged lepton processes in the light of existing and
upcoming experiments. Both of the models that do not allow proton decay from
renormalizable interactions have dimension five operators that, even if
suppressed by the Planck scale, can give rise to an unacceptably high level of
baryon number violation. We discuss symmetries that can forbid these dimension
five operators.
