Quinine is a medicinal tree from South America, and one of the 100 world’s worst invasive alien species of IUCN. The first quinine was brought to Java, Indonesia in 1854. By the 1930s Dutch plantations in Java produced 97% of the world's quinine, but now the most plantations were abandoned and spreading outside. We conducted a preliminary study to clarify the invasion of quinine to the montane forests on Mt. Tangkuban Perahu Nature Reserve (TPNR) and Mt. Gede Pangrango National Park (GPNP), West Java in July – September, 2011. Line transects were placed from its origin to the natural forest and three 100 m2 plots were located in both of its origin and the natural forest. In TNPR, the quinine spread 2500m with the average spreading rate 33.7 m/ year from the adjacent ex-quinine estate established in 1937. C. ledgeriana was only found in the natural reserve. C. pubescens spread into GPNP by 100m, 2000m, 300m in the northern, western, and southern part, respectively. The average of spreading rate was 6.3 m/ year in the northern part where the adjacent estate was established in 1995. In the southern part of GPNP, C. pubescens made a 6.4-ha dense stand. These results indicate the montane forests of Java have been invaded by quinine.