Disclosed are novel pyrazolo[3,4-d]pyrimidine derivatives that are inhibitors of Raf kinase. These compounds and their pharmaceutically-acceptable salts and esters are anti-proliferative agents useful in the treatment or control of proliferative disorders such as solid tumors, in particular breast tumor, colon tumor, lung tumor, prostate tumor, and melanoma. Also disclosed are a composition and a unit dose formulation comprising such a compound, or a pharmaceutically-acceptable salt or ester thereof, methods for making such compounds, and methods for using such compounds, or their pharmaceutically-acceptable salts or esters, in the treatment of proliferative disorders.