With regard to purchasing Tunisian IPOs shares, the current paper aims at considering two types of investors: a non-institutional investor and an institutional one. Each is concerned with placing a purchase order at the offer price during the subscription period. In line with the literature on IPOs, we attempted to determine the minimum price required by an investor allowing for recovering the initial investment, information costs, transaction costs, and the offsetting of shortfall. We expect that the initial return of an IPO share in the Tunisian market is positively related to the following factors: the number of non-institutional investors participating during the subscription period, the subscription ratio of institutional investors, the expected rate of return by investors, the gap between the closing date of the subscription period and the day following the announcement of the subscription result, the gap between the announcement of the subscription result and the first listing day, the number of trading days, the cost of information and the transaction costs. However, it is negatively related to other determinants, such as the discount level, the number of shares allocated for a non-institutional investor and the number of offered shares, which are allocated to non-institutional investors.