Fish bones are one of the most common foreign bodies in the upper aero-digestive tract. The use of plain X-ray in identifying fish bones has questionable value. We believe that the knowledge of the type of the fish ingested improves the diagnostic value of the neck X-rays. This study was designed to evaluate the relative radio-densities of the bones of commonly eaten fish in the UK. Twenty-three species of fish were studied and their bones were grouped into three depending upon their ratio-densities. This information is expected to be useful in identifying fish bones while reading plain radiography.