In 21 patients with initial signs of progressive systemic sclerosis, oesophageal motility was monitored manometrically from the start of D-penicillamine treatment and over a period of up to 5 years. Urinary excretion of the collagen-specific amino acids hydroxyproline and hydroxylysine, and of proline was used as a guideline for monitoring the bioavailability of D-penicillamine. D-penicillamine therapy was found to be unable to arrest the progress of oesophageal involvement. A downward trend over time--statistically significant at p = 0.03, p = 0.02, and p less than 0.005--was found for lower oesophageal sphincter pressure, peristaltic wave pressure in the distal third, and peristaltic wave pressure in the middle third of the oesophagus, respectively.