The radiological signs of transient tachypnoea are analysed via a study conducted with 9 children suffering from this disturbance of respiratory adaptation. The main signs are reticulonodular structural increases on both sides and extended vessels with unsharp outlines; to a lesser extent, marked small interlobar fissure, signs of an expiratory disturbance of ventilation, and cardiomegaly are seen also. Differentiation against hyaline membranes is easy and delineation against pneumonic and haemorrhagic infiltrations is usually not at all difficult. However, it may be less easy to differentiate between a relatively severe transient tachypnoea and cardiac left decompensation, since the radiological signs resemble each other. Assessment of a chest x-ray film of the newborn should be evaluated in such cases only if the clinical pattern of signs is known, since this is the only way to obtain adequate radiological clarification.