Information asymmetry between owners and managers exists in the corporate form of business organization. This leads to potential adverse selection for new stockholders and for new lenders. Information asymmetry also fosters the incidence of moral hazards. These place existing owners and creditors at risk. Even in the absence of such excesses, communication of corporate activity is a thorny problem. For reasons such as these, the extent and frequency of disclosure is a subject of intense interest. This article adds to the overall understanding of corporate disclosure by identifying some elements of activity that managers are willing to divulge in periods shorter than the annual accounting period. The sample includes all non-finance/insurance sector firms listed on the Helsinki Stock Exchange over the period 1985-93. This venue accommodates the recommendation made in the literature that the determinants of periodic reporting be studied in a current European context. The class and number of owners, business risk, growth potential, size and regulatory environment are all found to influence strictly voluntary interim disclosure.