  We investigate the possible regular solutions of the boundary Yang-Baxter
equation for the vertex models associated to the D_{n+1}^(2) affine Lie
algebra. We have classified them in terms of three types of K-matrices. The
first one have n+2 free parameters and all the matrix elements are non-null.
The second solution is given by a block diagonal matrix with just one free
parameter. It turns out that for n even there exists a third class of K-matrix
withou free parameter.
