In the standard portfolio problem, a shift in the distribution of the
risky asset is ''portfolio-dominated'' if it reduces the demand for th
e risky asset by all risk-averse agents, irrespective of the risk-free
rate. We show that the condition obtained by Landsberger and Meilijso
n (1993), while necessary, is not sufficient for portfolio dominance a
nd we present an exact necessary and sufficient condition.