We propose new techniques for efficient breadth-first iterative manipulation of ROBDDs. Breadth-first iterative ROBDD manipulation can potentially reduce the total elapsed time by multiple orders of magnitude compared to the conventionaldepth-first recursive algorithms whenthe memory requirementexceedsthe availablephysical memory. However, the breadth-first manipulation algorithms proposed so far [5] have had a large enough overhead associated with them to make them impractical. Our techniques are geared towards minimizing the overhead without sacrificing the speed up potential. Experimental results indicate considerable successin that regard. 1 Drawbacks of Conventional DF Recursive ROBDD Manipulation There is a need today for manipulating ROBDDs with tens to hundreds of millions of nodes which cannot be met by means of conventional depth-first (DF) recursive algorithms. There are two good reasons why DF recursive algorithms have been the algorithms of choice for ROBDD manipulation u...