The study of wet biological tissuesin situusing the electron microscope was made possible by modifying existing replica techniques and developing a new wet replication method. The shortcomings of existing replica techniques are discussed and the modifications necessitated are described.Replicas of wet tissues were produced in extremely thin polystyrene films which could be observed directly in the electron microscope; however, superior results were obtained by preparing silica replicas from the replicated polystyrene films. A modified two‐replica silica method proved satisfactory but the three‐replica silica method developed was preferable. Electron micrographs of wet wood fiber surfaces used to illustrate these techniques reveal new data concerning submicroscopic cell wall structure.The problem of interpreting replicas of partially degraded and disorganized materials is illustrated and discussed briefly.