We have used atomic force microscopy to study tobacco mosaic virus deposited on mica by the evaporation of films of dilute solutions of TMV. Solutions of TMV in distilled deionized water deposit TMV aggregates similar to those seen by electron microscopy on other substrates. However, solutions containing both TMV and bovine serum albumin (BSA) deposit unaggregated, randomly oriented TMV rods. High-resolution AFM images taken under 2-butanol reveal that numerous BSA molecules are attached to each TMV rod. We think that the attachment of BSA particles to TMV rods changes the intervirus interactions and results in dispersed TMV both in solution and on mica.