AbstractSnakehead fish of the genusChannahave well‐developed air‐breathing organs (ABO) yet retain their gill arches for respiratory and non‐respiratory functions. Alterations in the macrocirculation accompany inclusion of the ABO and appear to enhance gas exchange efficiency (Munshi et al., 1994. Anat. Rec. 238:77–91). In the present study, the microcirculatory anatomy of gill and ABO from two facultative air‐breathingChanna, C. punctataandC. gachua, and one obligate air‐breather,C. marulius, were examined in detail using scanning electron microscopy (SEM) of vascular corrosion replicas and fixed whole‐sectioned tissue. The results show that the circulation in the filaments from the first, second, and third gill arches is similar to that found in water‐breathing teleosts. Fourth gill arch microcirculation ofC. punctatais not different from the other three, whereas inC. marulius, it has been greatly modified into a network of low‐resistance vascular shunts, although remnants of an intralamellar filamental microcirculation remain. The vascular shunts are formed from extensions of afferent and efferent lamellar arterioles and the complete, or nearly complete, loss of a lamellar sinus. The vasculature of the ABO has been highly modified in all species into a coiled‐spiral capillary network with a constricted aperture guarding a dilated capillary dome at the epithelial surface. Microvilli are found congregated on the aperture endothelium ofC. punctatabut they are virtually absent fromC. maruliusendothelium. Less than 15% of the ABO capillary surface appears to face the epithelium and thereby contributes directly to gas exchange. These findings suggest that the microvascular modifications observed inChannaentail more than a simple increase in the contact surface between ABO vessels and air and they may serve other unknown physiological functions. ©