AIM:To compare the long-term effect of succimer (Suc) with that of penicillamine (Pen) in treating hepatolenticular degeneration (HLD).METHODS:One hundred and twenty patients with HLD were divided into 2 groups. Group A (n =60) received Suc 750mg,po.bid.Group B (n =60) received Pen 250mg, po. qid. The period of maintenance treatment varied from 6 months to 3 years, averaging 1.5 years. Symptoms and therapeutic effects were evaluated by modified Goldstein scale.RESULTS:The total effectiveness of group A in two different periods of treatment were 80% and 85% respectively, higher than those of group B (58% and 59% respectively)(P < 0.05). Suc also had obvious curative effects for the patients who failed in the use of Pen. There were fewer side effect in group A than in group B (P < 0.05). Suc and Pen could increase urinary copper excretion effectively and continually.CONCLUSION:Suc is more effective and safer than Pen. Clinically, it can replace Pen as first-choice drug for long-term maintenance therapy of HLD.