Penicyllamin is a useful drug in the treatment of some cases of severe rheumatoid arthritis, or in unsuccessful therapeutics. 2. It can lead to remission or to antiinflamatory activity from 20 to 40%. 3. It has a high percentage of iatrogenic effects, but they are generally slight and in a minor percentage the alterations are severe (hematological mainly). 4. Its use requires: a) Correct prescription. b) Careful clinic and paraclinic observation. c) Experience and knowledge in rheumatologic speciality. 5. It may be of use in other connective tissue diseases or in immunological processes with disfavorable consequences to the organism.