The paper presents a new image denoising method for impulse noise in grayscale images using a context-based prediction scheme. The algorithm replaces the noisy pixel with the value occurring with the highest frequency, in the same context as the replaceable pixel. Since it is a context-based technique, it preserves the details in the filtered images better than other methods. In the aim of validation, we have compared the proposed method with several existing denoising methods, many of them being outperformed by the proposed filter.