This study explores the role of direct real estate investment in a portfolio context incorporating the real estate imperfections of indivisible assets and no short sales. Mean-variance efficient portfolios are calculated using Treasury-bills, bond and equity indices together with cash flows and appraised values from a set of twenty-two properties having an aggregate appraised value of $336 million. Real estate diversification benefits are shown to be the greatest with smaller properties and are most advantageous at higher target levels of return. The study suggests that a 9% allocation to real estate is optimal, rather than the 20% figure suggested in other studies.