The Most Similar Neighbor (MSN, Moeur and Stage 1995) program is used to impute attributes measured on some sample units to sample units where they are not measured. In forestry applications, forest stands or vegetation polygons are examples of sample units. Attributes from detailed vegetation inventories are imputed to sample units where that information is not measured. MSN performs a canonical correlation analysis between information measured on all units and the detailed inventory data to guide the selection of measurements to impute. This report presents an introductory discussion of Most Similar Neighbor imputation and shows how to run the program. An example taken from a forest inventory application is presented with notes on other applications and experiences using MSN. Technical details of the way MSN works are included. Information on how to get and install the program and on computer system requirements is appended.