Experiments were initiated to screen an efficient plant bioregulator (PBR) for promoting fruit set of Ardisia pusilla in 2004 and to determine suitable concentration and treating time of a selected PBR in 2005. Three PBRs such as mepiquat chloride (MC), ρ-chlorophenoxyacetic acid (4-CPA), and N-(2-chloro-4-pyridyl)-N'- phenylurea (CPPU) were investigated for fruit set promotion. Plant growth and fruit set of one-year-old rooted cuttings foliar-sprayed with the three PBRs at each four concentrations on May 5, 2004 (about 50% flowering stage) were examined on November 11, 2004. Comparing fruit set of the control (14.9%), CPPU treatments showed the highest fruit set (45.0%) among the three PBRs and stable responses of fruit set regardless of its concentrations (2.5?20 ㎎ㆍL?¹). Thus, CPPU was re-evaluated for fruit set promotion in 2005, dividing foliar-spraying time by three flowering stages (20, 50, and 80%) from May 30 to June 13. CPPU treatment at 80% flowering level was the most effective in fruit set promotion than those at other levels regardless of its concentrations (5?20 ㎎ㆍL?¹). Fruits obtained from all treatments produced 100% normal seeds and seed germination percentages did not show significant difference between all PBRs and control. In conclusion, CPPU was found to be an efficient fruit set promoter of A. pusilla due to high fruit set and constant stability regardless of its concentrations. Moreover, A. pusilla plants treated with CPPU did not produce any seedless fruit related to parthenocarpy, which is generally found in several horticultural crops after this PBR application.