The effects of chelidonine, a benzophenanthridine isoquinoline alkaloid, on L-DOPA-induced cytotoxicity in PC12 cells were investigated. The treatment of PC12 cells with chelidonine $(1-4;{mu}M)$ decreased dopamine content in a dose-dependent manner (30.2% inhibition at $4;{mu}M)$. Chelidonine was not cytotoxic up to $4;{mu}M)$. However, chelidonine at concentrations higher than $5;{mu}M$ caused a cytotoxicity in PC12 cells. L-DOPA at concentrations higher than $50;{mu}M$ led to cell damage by oxidative stress in PC12 cells. Chelidonine at non-cytotoxic concentration ranges of $1-4{mu}M$ aggravated L- DOPA $(20-50;{mu}M)$-induced cytotoxicity in PC12 cells. The L-DOPA-induced cytotocxicity was synergistically stimulated by chelidonine at concentrations grader than $5;{mu}M$. These data demonstrate that chelidonine exacerbates L-DOPA-induced cytotoxicity. Therefore, it is proposed that the long-term L-DOPA therapeutic patients with chelidonine may need to be checked for the adverse symptoms.