Nuveen Premium Income Municipal Fund 4, Inc. (the Fund) is a closed-end management investment company. The Fund seeks to provide current income exempt from regular federal income tax by investing primarily in a portfolio of municipal obligations issued by state and local government authorities or certain United States territories. The secondary investment objective is the enhancement of portfolio value. The Fund invests in municipal securities that are exempt from federal income taxes. The Fund invests at least 80% of its managed assets in municipal securities rated investment grade (Baa/BBB ) at the time of investment, or, if they are unrated, are judged by the manager to be of comparable quality. The Fund may invest up to 20% of its managed assets in municipal securities rated below investment quality or judged by the manager to be of comparable quality, of which up to 10% of its managed assets. The Fund's investment advisor is Nuveen Asset Management.