Abstract: Proportionate-type affine projection algorithms were developed in the context of echo cancellation, as a generalization of the proportionate-type normalized least-mean-square algorithms. A matrix inversion is required within the affine projection algorithm (APA). In the case of proportionate-type APAs, the update of the matrix to be inverted is very computationally expensive. In this paper, an efficient update of this matrix is proposed and the procedure is applied for a recently developed proportionate-type APA. It is shown that the proposed algorithm achieves similar performance but significantly lowers numerical complexity as compared to known proportionate-type APAs.