Controlling crystal habit using growth modifiers provides novel avenues for tailoring properties of crystalline materials. Here, we report on the design of a high-throughput screening assay for rapid identification of growth modifiers using calcium oxalate monohydrate crystallization as a model system. We conducted a systematic study of assay parameters (sample volume, shaking, and temperature) on crystallization kinetics. Crystallization half-time (t(1/2)), defined as the time at which crystallization is 50% complete, was obtained from the logistic fit of kinetic data and used as a measure of growth modifier potency. A test library of 13 peptides composed of aspartic acid and alanine residues was screened to determine their growth promotion or inhibition potentials. Leads identified from this study are in good agreement with ion-selective electrode measurements and a single time point measurement of free calcium ion concentration is an excellent end-point for evaluating modifier potency. (C) 2016 American Institute of Chemical Engineers AIChE J, 62: 3538-3546, 2016