Hydrolysis of the whey protein alpha-lactalbumin with a specific serine protease has been shown to result in regular nanotubes of approximately 20 nm in outer diameter and reaching several mum in length. Tubular assembly depends on the concentration of protein as this determines how far the hydrolysis proceeds. A concentration of 30 g L(-1) is a prerequisite for tubular formation, as is a minimum concentration of calcium. At lower protein concentrations calcium-independent formation of linear fibrils (approximately 5 nm in diameter) is favoured. Possible applications of alpha-lactalbumin nanotubes include use as a viscosifier and gelling agent and also pharmaceutical utilization (such as targeted drug release) and use in nanotechnology can be envisioned.