The study is primarily concerned with the verification, and subsequent explanation, of the existence of the phenomenon of new issue underpricing. The primary purposes of the research conducted in this study were to: (1) determine if investors may earn excess returns on new issues by purchasing at the prevailing market price in the immediate after-market rather than at the offer price, (2) develop a simultaneous equation model to explain underpricing, percentage cash spread, and the relationship between the two using various firm, issue, and market characteristics, and ( 3) analyze the effects of institutional constraints concerning percentage cash spread on the relationship between underpricing and percentage cash spread. The examination of excess returns indicates that efficiency prevails in the new issues market beginning with the second trading day. Therefore, investors purchasing new issues in the immediate after-market may expect to not earn excess returns. The results of the estimation of the econometric model using the entire sample of new issues does not indicate a simultaneous relationship between underpricing and cash spread. However, in order to analyze the effects of the institutional constraint on percentage cash spread, it is hypothesized that the most severely underpriced issues are most seriously affected by constraint. The sample is divided into quartiles on the basis of magnitude of underpricing and the econometric model is estimated separately for each quartile. The upper quartile exhibits a recursive relationship suggesting that percentage cash spread is first set and underpricing is adjusted accordingly to lessen risk of distribution and thereby compensate for the lower level of percentage cash spread. A simultaneous relationship does occur in the middle quartiles, but the relationship is positive indicating that higher percentage cash spread offerings also experienced greater underpricing. These results furnish evidence that new issues are affected by institutional constraints on percentage cash spread and the guidelines could be the cause of a portion of the underpricing occurring in the new issues market. / Ph. D.