A shoe insert for adjusting the fit of a shoe on a person's foot, and the combination of such insert and a shoe with elements providing for removable securement of the insert within the shoe. The shoe insert may be formed from a stable, resilient, and biodegradable material such as a molded mixture of polyurethane and cork, and may be removably secured within the shoe via a cooperating slot and rail system to prevent slippage of the insert within the shoe. The shoe or insert or both may be contoured to provide a custom anatomical fit to the person's foot.