In this paper, we report the effects of mixing intensity, seeding, composition of baffle material and final temperature on meta-stable zone width (MSZW) and crystal polymorph in solution crystallization of an industrially important compound, l-glutamic acid, in an oscillatory baffled crystallizer (OBC). The results show that the MSZW decreases with increasing of mixing; meta-stable alpha crystals are transformed into stable beta crystals with enhanced mixing intensity. Seeding meta-stable alpha crystals in operational conditions that promote beta crystals leads to the formation of alpha crystals allowing co-existence of both forms; while seeding stable beta crystals in conditions that favour alpha form allow beta crystals prevailing in all conditions. Smoother surface of baffle material in OBC exhibits larger MSZW and favours meta-stable crystals, while rougher surface has smaller MSZW with stable crystals dominating. The meta-stable crystals gradually change into the stable form when final cooling temperature is closer to its nucleation temperature. The outcomes from this work indicate that by controlling process parameters desirable crystal polymorph can be obtained in the OBC. (C) 2009 Elsevier B. V. All rights reserved.