Bronnocriptine was administered to 66 patients with advanced Parkinson disease (PD) and increasing disability despite optimal treatment with levodopakarbidopa (Sinemet®). Forty-five patients tolerated at least 25 mg per day of bromocriptine (the “adequately treated” group) in addition to Sinemet and had significantly decreased rigidity, tremor, bradykinesia, gait disturbance, and total score, but increased involuntary movements. Twenty-five of these 45 patients improved by at least one stage. Among the 45 patients, 27 had “on-off” effects, and in 19 the “on-off” effects decreased on bromocriptine. The mean dose ofbromocriptine in adequately treated patients was 47 mg, permitting a 10 percent reduction in the dose of levodopa. Twelve adequately treated patients received bromocriptine for at least 1 year, and 8 continued for longer than this. Bromocriptine was discontinued in 29 of 66 patients because of adverse effects, including mental changes (14 patients) and involuntary movements (9 patients). All adverse effects were reversible. Despite adverse effects, expense, and scarcity, bromocriptine, when added to levodopa, is useful in patients with advanced disease who no longer respond satisfactorily to levodopa, and for whom no other treatment is available.