Degradation of preelastic fibres (oxytalan and elaunin) and mature elastic fibres by human leukocyte elastase (HLE) was investigated using automated image analysis. Specimens from two young healthy adults were used. Although HLE hydrolyzed both fibre types, mature elastic fibres exhibited greater susceptibility to this effect than preelastic fibres. Avocado and soybean unsaponifiables are widely prescribed in rheumatology and parodontology and have also been the focus of ex vivo experiments aimed at determining whether they protect elastic fibres against degradation by HLE. Findings from the present study indicate that avocado and soybean unsaponifiables protect all types of gingival elastic fibres from degradation by HLE. Avocado and soybean unsaponifiables may be beneficial in patients with gingival inflammation and parodontitis, since HLE plays a major role in these disease states.