Novel monolithic catalyst supports with regular three-dimensional structure and channel-to-channel interconnectivity have been fabricated using a direct ceramic fabrication technique known as "robocasting". Using the oxidation of CO over a Pt/gamma-Al2O3 catalyst as a probe reaction, we have quantified the mass transfer over several new geometries and compared them to traditional straight-channel monolithic supports. A geometry of alternating rods that presents no line-of-sight flow paths and about 45% void volume increases the dimensionless Sherwood number by a factor of 3 over that of traditional honeycomb supports. However, the resulting pressure drop is similar to that of a packed bed (up to a 1000-fold increase). A similar robocast structure with 74% void volume improves the Sherwood number by a factor of about 1.5 relative to the honeycomb geometry but only increases the pressure drop by a factor of 4. The results illustrate that robocasting technology affords an unprecedented degree of freedom, allowing optimization of ceramic monoliths for specific applications.