This paper presents an analysis of the effects that Austria's accession to the EU had on several key financial ratios of small business firms in the retail and wholesale trade sectors. These two industries were selected because before 1995 they were protected in many respects, thus vulnerable to increased competition after accession. The financial ratios selected are cash-flow per employed person, mean absolute deviation of cash-flow per employed person (as a variation-based risk measure), debt per employed person and financing cost as percentage of external debt. Together these four ratios determine a firm's creditworthiness. Our study is unique in that it is based on micro data, which allows us to consider the whole distribution of the ratios as compared to only aggregates as in other studies and to examine the scale effects within idustries. The data basis are balance sheets of more than 14,000 retail and 8,000 wholesale trade firms of all size classes during 1989-1996. In the empirical analysis we test the hypothsis of a structural break in the year of Austria's accession to the EU and put particular emphasis on the question whether small and large firms were affected differently by that structural break.