The morphology of thiacarbocyanine and oxacarbocyanine dye J-aggregates adsorbed on (001) surfaces of AgBr microcrystals grown in gelatin was observed by atomic force microscopy. No residue of fibrous gelatin was found on the specimen. The cyanine dyes grew in islands or stripes by means of the Volmer- Weber growth mode, rather than by monolayer adsorption. The thickness of stripes varied from 0.5 nm (monolayer) to 30 nm, and the stripes were constructed of many rectangles [20 ×(35−50) nm]. The rectangles were regarded as elementary crystallites or J-aggregate particles photoelectrically separated from one another.