Cross sectional echocardiography can provide accurate anatomical diagnosis in congenital heart diseases and therefore should be able reliably to identify criss cross hearts and enable the analysis of their sequential arrangement non-invasively. The cross sectional echocardiographic diagnoses in eight consecutive patients with this condition were compared with those made at cardiac catheterisation and cineangiocardiography (five retrospectively, three prospectively). The mean number of invasive studies required to reach the diagnosis was 1.9 (range 1-4). Complete anatomical diagnosis was achieved with cross sectional echocardiography in all patients, but identification of ventricular morphology was much more straightforward using cineangiocardiography. If the transducer was held steady in either a precordial or subcostal position and rocked anteriorly and posteriorly the characteristic crossing over of the ventricular inflows could easily be seen. In no plane was there normal parallel arrangement of ventricular inflows. A complete diagnosis should be possible in these patients using cross sectional echocardiography in experienced hands and at a single session in the cardiac catheterisation laboratory.