Expandable radiocollars, designed to monitor juvenile survival and movements, were placed on 132 neonatal elk (Cervus elaphus) in Yellowstone National Park during 1987-1990. A modified design of the same collar was placed on 164 neonates of the Jackson elk herd in northwest Wyoming during 1990-1992. One of the Yellowstone calves and 19 of the Jackson calves cast their collars before 15 July of their birth year. General deterioration of collar materials resulted in loss of the Yellowstone collars 12-18 months post-deployment. Separation of breakaway tabs resulted in loss of 13 collars from Jackson elk 504 ?? 60 days post-deployment, but the remaining collars remained on elk for ???4 years. These light-weight and adaptable collar designs achieved study objectives. We provide design recommendations for future monitoring of juvenile elk.