Evolutionary approaches to enzyme engineering can be powerful tools in the search for biocatalysts with practical utility, and the diversity of desirable enzyme activities and properties continues to drive development of new high throughput functional screens.  While many of these techniques benefit from cutting edge technologies, others may be creative adaptations of well studied and simplistic assays.  This point will be emphasized via a discussion of two disparate methods for screening recombinant enzyme libraries.  First, the technical challenges faced by researchers seeking to leverage the speed and quantitative nature of flow cytometry will be introduced.  In particular, the high diffusivity of soluble enzymatic reaction products can limit the utility of this fluorescence based single cell assay technique.  In vitro compartmentalization technology provides one means of overcoming this problem, and has been used to engineer a fungal hydrolase for improved activity towards esters of pharmaceutical compounds.  In contrast to this technically challenging use of high-end instrumentation, a novel modification of radial diffusion antibiotic assays will also be presented.  Utilizing the flexibility inherent to this simple assay system, libraries of antimicrobial polypeptides may be screened for biocidal activity towards a variety of clinically relevant targets.  The unique advantages of each method, with respect to the different enzyme systems, underscores the importance of maintaining a diverse toolbox of screening technologies capable of satisfying the demands of various enzyme targets.