  Baryogenesis from the coherent production of a scalar condensate along a flat
direction of the supersymmetric extension of the standard model (Affleck-Dine
mechanism) is investigated. Two important effects are emphasized. First,
nonrenormalizable terms in the superpotential can lift standard model flat
directions at large field values. Second, the finite energy density in the
early universe induces soft potentials with curvature of order the Hubble
constant. Both these have important implications for baryogenesis, which
requires large squark or slepton expectation values to develop along flat
directions. In particular, the induced mass squared must be negative. The
resulting baryon to entropy ratio is very insensitive to the details of the
couplings and initial conditions, but depends on the dimension of the
nonrenormalizable operator in the superpotential which stabilizes the flat
direction and the reheat temperature after inflation. Unlike the original
scenario, an acceptable baryon asymmetry can result without subsequent entropy
releases. In the simplest scenario the baryon asymmetry is generated along the
$LH_u$ flat direction, and is related to the mass of the lightest neutrino.
