This paper examines the extent, and determinants, of daily seasonality in the Dublin stock exchange over a ten-year period. It is found that there is a daily seasonal pattern in the two main indices. However, this seasonal pattern is mid-week, contrary to the previous research. This mid-week seasonality appears, on investigation, to differ in its source as between financial and other firms. Financial firms appear to react to macroeconomic news and non-financial to firm specific news, albeit weakly. No support for microstructural hypotheses of daily seasonality is found.