Scanning and transmission electron-microscopy have been applied for study of the ultrastructural features of the blood-bubble interface in the vasculature of explosively-decompressed rats. In scanning electron-microscopy, the surface facing the bubble appeared smooth, with slight undulation and frequent roundish protrusions. In cross sections of the material between the bubbles, there could be observed a continuous surface layer facing the bubble, a loosely-bound meshwork of fibrous material, and extreme congestion of erythrocytes. In transmission electron-microscopy there were found alignment of platelets along the interface, and a thin (10-20 nm) layer of osmiophilic material, in accordance with earlier ultrastructural studies. The platelets were often rounded. It is concluded that the initial phase of the blood-bubble interaction is the deposition of a plasma protein coat, followed by the attachment platelets, possibly related to activation of the coagulation system.