One hundred Indonesian plant extracts were screened to investigate their effects on the P-glycoprotein (P-gp) activity in human uterine sarcoma cells, MES-SA/DX5, for the first time. Among others, four samples, Alpinia galanga (BuOH ext.), Sindora sumatrana $(CHCl_3;ext.)$, Strychnos ligustrina $(CHCl_3;ext.)$, and Zingiber cassumunar Roxb (hexane ext.), exhibited the most potent inhibition on the P-gp activity. They increased cytotoxic activity of daunomycin up to $IC_{50}$ values of less than $1.41;{mu}M$, which is a value with a positive control, verapamil. Other 25 samples showed significant P-gp inhibitory activity with $IC_{50}$ values between 1.4 and $4.0;{mu}M$. These prospective samples will be subjected to further laboratory phytochemical investigation to find active principles.