We have compared the capillary tube assay for migration inhibition studies with our modification of the agarose microdroplet technique, using several sources of factors with inhibitory activity (lymphokines, bacterial factors) and a variety of cell types (inflammatory exudate cells, tumor cells). In all circumstances both procedures gave quantitatively similar results, and high statistical correlation was found. These results suggest that the two procedures are measuring similar properties, and in any case may be used interchangeably as assays.