One of the obstacles limiting the application of electrospun scaffolds for tissue engineering is the nanoscale pores that inhibit cell infiltration. In this article, we describe a technique that uses ice crystals as templates to fabricate cryogenic electrospun scaffolds (CES) with large three-dimensional and interconnected pores using poly(D,L-lactide) (PLA). Manipulating the humidity of the electrospinning environment the pore sizes are controlled. We are able to achieve pore sizes ranging from 900 +/- 100 mu m(2) to 5000 +/- 2000 mu m(2) depending on the relative humidity used. Our results show that cells infiltrated the CES up to 50 mu m in thickness in vitro under static culture conditions whereas cells did not infiltrate the conventional electrospun scaffolds. In vivo studies demonstrated improved cell infiltration and vascularization in the CES compared with conventionally prepared electrospun scaffolds. In gaining control of the pore characteristics, we can then design CES that are optimized for specific tissue engineering applications. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 91A: 231-240, 2009