Natural rubber latex films were soaked in potassium hydroxide solution of various pH. The effects of soaking on the crosslink density, extractable protein content and tensile properties of the films were investigated. Potassium hydroxide solution was believed to be effective in reducing extractable protein content by leaching out the extractable protein from natural rubber latex films. Results showed that crosslink density and the extractable protein content of the films reduced with increasing pH of the KOH solution. The tensile properties, except elongation at break, reduce when pH of KOH solution is above 12. Extractable protein content was reduced especially when the pH of the solution was greater than 12.0.