Concanavalin A (Con A), 25 microgram/ml in the tetrameric form, inhibits migration and differentiation of cultured amphibian neural crest. Affected cells loose their angulated morphology and become rounded. A correlation exists between the lectin treatment and the overall cellular and stress fiber morphology. We describe a quick, simple method for disclosing the stress fiber system using fluorescence microscopy after staining with 1% alcoholic eosin.