This paper studies the evolution of auditing in Portugal, in an historical, legal and empirical perspective, since monarchy to the present day. This historical development began with the Código de Comércio published in 1888(Commerce Law), the first law that focused on independent surveillance of public limited companies.The economical and social context of the emergence of the auditor (Revisor Oficial de Contas), and the pattern adopted will also be commented. The present position of the profession is analyzed in an empirical study on the structure of the market demand and the offer, as well as the concentration of the statutory audit market in Portugal. In this analysis, we used data provided by Institute of Statutory Auditors (OROC), and reached the conclusion that the statutory audit market in Portugal, in the four years prior to the general use of the point system, from 2001 to 2004, a concentration tendency regarding listed and unlisted companies, was shown.