Very few people receive a job offer after a first interview. Therefore, it is very important to follow up with the prospective employer. It is a good idea to follow up the interview with a thank letter. This fixes on the prospective employer's mind a clear image of you as a competent, qualified, interesting person. He may interview numerous people, all of whom begin to fade into an indistinguishable blur after a while. Your letter can remind him of your interest and add information you may have omitted. Your persistence in doing so may be the very factor that prompts an invitation for subsequent interviews as well as allow you to maintain contact and possibly more job leads. Be warned, however, if it is not a carefully written, carefully thought through letter, its effect may be the opposite of the intended purpose.