many others. For the case of macromolecules such as in protein crystallization, kinetic data of continuous growth has only been presented for lysozyme [15, 27, 28]. Very recently, quantitative data for both the classical layer-by-layer growth mechanism and the kinetic roughening regime for the crystallization of glucose isomerase from Streptomyces rubiginosus have been presented [16]. In this paper we show that kinetic roughening-like transitions in the presence of a fi- nite nucleation barrier can occur owing to kinetic mechanisms still rendering possible the transition from slow layer-by-layer growth regime (low supersaturations) to a fast continu- ous growth regime (high supersaturations). The general scheme used views the process of crystal growth at constant temperature driven by the difference in chemical potential of the solution around the crystal surface and the reservoir of the surrounding liquid phase. The local environment around the surface incorporates the barriers, kinks and dislocations while relevant kinetic processes such as absorption, surface diffusion and nucleation contribute to the growth. A mean field model and a Monte Carlo simulation are proposed and serve as an illustrative generic explanation of the observed data from protein crystallization [16]. In Section II a minimal mean field model is developed incorporating cluster formation and possessing the two main asymptotic regimes, exhibiting the transition from low to high supersaturation growth. In Section III we investigate an extension of a “solid to solid” (SOS) Monte Carlo simulation linked to, but more general than, the mean field model, and accounting for kinetic roughening in the presence of finite nucleation barrier and dislocations. The main conclusions are summarized in Section IV. Our mean-field model of crystal growth is based on a generalization of the Burton- Cabrera-Frank model for epitaxial growth[7, 29, 30] and is also motivated by theoretical work hinting at a competition between surface aggregation and the formation of cluster by direct incorporation of material from solution[31]. Let X$_{0}$ and X denote, respectively, II. MEAN FIELD MODEL 3 Large reservoir ⇋ Local environment ⇌ desorption Surface: absorption, surface diffusion, around surface nucleation, growth