当一家公司决定通过销售股票和债券来筹措长期资金，它必须找到买主。要是没有投资银行，做这件事就非常困难。投资银行的主要功能就是为公司销售长期证券。投资银行是公司与投资者之间的中介人，他一旦同意承销一家公司的债券或股票，它就要承担包销的责任。
Briefly4, the procedure for raising new long-term funds is as follows. The company seeking funds approaches the investment banker, who in turn investigates the company to find out about its financial and technical prospects5. An investment banker who underwrites a security guarantees the corporation a certain price for the securities. For example, if it is believed that a bond issue of $ 20 million can be sold at par6, the investment banker may offer to underwrite the issue at $19 million. The corporation is guaranteed this amount, and the investment banker takes the risk of selling the issue. If the issue is indeed sold at par, the banker will make a gross profit of $1 million.
简言之，筹措长期资金的步骤如下：筹措资金的公司与投资银行接洽，投资银行又反过来对该公司基本面及财务状况进行调查。承销证券的投资银行为公司发行的证券承诺一定的发行金额。例如，如果他们认为，2000万的债券发行额可以按照票面价格出售，投资银行将以1900万的金额包销。发债公司被确保得到这笔金额，投资银行承担了包销的风险。如果发行的债券确实按照票面价格出售了，该投资银行将获得100万的毛利。
If a particular issue is so large that the banker cannot handle it all or does not want to assume all the risk, other investment bankers may be asked to participate in the offering by forming a syndicate. Sometimes as many as a hundred investment bankers form a syndicate to handle a single large securities offering.
如果某种证券发行额很大，投资银行不能包销，或不愿承担全部风险，它就可以邀请另外一些投资银行组成辛迪加，参与证券发行。有些时候，会有一百家之多的银行组成一个辛迪加来共同包销一笔金额巨大的证券发行
