Eighteen patients with a variety of depressed scars, predominantly as a result of acne, were treated with a purified bovine dermal collagen prepared as an injection (Zyderm I) for direct implantation into the scars. Both subjective and objective assessment showed encouraging results in those with soft and distensible scars. This method is, however, largely unsuitable for rigid, fibrotic or ice-pick scarring. Any improvement was usually apparent by the third treatment session. This is a safe, virtually painless, simple technique requiring no specialized equipment and has a high patient acceptability-but is expensive.