David C. Brydges and John Z. Imbrie Branched Polymers and Dimensional Reduction (53K, latex with 3 ps figures) ABSTRACT. We establish an exact isomorphism between self-avoiding branched polymers in D+2 continuum dimensions and the hard-core continuum gas at negative activity. We review conjectures and results on critical exponents for D+2 = 2,3,4 and show that they are corollaries of our result. We explain the connection (first proposed by Parisi and Sourlas) between branched polymers in D+2 dimensions and the Yang-Lee edge singularity in D dimensions.