Biodegradable and biocompatible porous scaffolds characterized by a substantially continuous polymer phase, having a highly interconnected bimodal distribution of open pore sizes with rounded large pores of about 50 to about 500 microns in diameter and rounded small pores less than 20 microns in diameter, wherein the small pores are aligned in an orderly linear fashion within the walls of the large pores. Methods of preparing polymeric tissue scaffolds are also disclosed.