A newly collected historical database for the Helsinki Stock Exchange (HSE) is used to analyse the number and structure of listed equity securities. The analysis shows that from its establishment in October 1912 to the end of 1981, a total of 849 different stock series and related issue rights have been listed on the HSE. Of these, 206 are normal stock series and they represent 167 different companies. The two largest industries represented on the HSE during most of the analysed period are metal and manufacturing and pulp and paper industries. Together they represented more than half of the listed companies throughout most of the sample period.