The Basel Committee designed a system of risk weights (“standardised approach”) to measure the riskiness of banks' loan portfolios. We investigate its ability to adequately reflect risk through an analysis of the economic capital implied in corporate bond spreads. This is based on a dataset of issuance spreads, ratings and other relevant bond variables including 7232 eurobonds issued by an internationally-diversified sample during 1991–2003. Three main results emerge: the spread/rating relationship is strongly significant; the estimated spreads per rating class indicate a steeper risk/rating relationship than the one approved by the Basel Committee; no significant difference appears in the spread/rating relation of banks and non-financial firms issuers.