Inactivated Sendai virus was used to investigate a stress response in 3T3-LI cells. The results were studied using immunohistochemistry and Western blotting techniques. Sendai virus infection caused collapse of the intermediate filament (IF) network, from the cell periphery towards the perinuclear region. This process was complete within two hours. During this time the virus particles were seen to accumulate around the nucleus. After four hours, the IF had begun to recover their normal distribution, wherease the virus remained in the perinuclear region. Sendai virus was not detected in the cytoskeleton fraction of the cells by Western blotting. This may be due to practical difficulties. The viral infection, and subsequent IF collapse did not cause an increase in the amount of ubiquitin conjugates in the cytoskeletal fraction. Anti-ubiquitin immunohistochemistry also showed no change in ubiquitin levels or distribution in the cells after viral infecton.