Ubiquitin-protein conjugates and alpha B crystallin are detected immunohistochemically in cells undergoing extensive morphological reorganisation in early chicken embryos. Cytoplasmic ubiquitinated proteins and alpha B crystallin are coordinately found in cells of the lens, notochord and myotome. The antigens appear in the myotome cells precisely at the point at which the cells begin to migrate from the dorsomedial lip of the dermamyotome. The findings indicate that ubiquitin and alpha B crystallin may have a coordinate role in the extensive architectural remodeling which occurs in these developing tissues in the early chick embryo. Some form of functional association between protein ubiquitination and alpha B crystallin in cells may explain why alpha B crystallin is found with ubiquitin-protein deposits in some neurodegenerative diseases.