Ikelle, L.T., 2016. Up-down separation of OBS wavefield using ICA techniques. Journal of Seismic Exploration, 25: 419-432. We here describe an effective way of performing up-down separation of OBS wavefield. The key feature of the up-down separation is the decomposition matrices. We will also name them mixing matrices. These matrices describe how upgoing and downgoing wavefields have been combined to produce the multicomponent data that we record. The inverses of these matrices allow us to decompose multicomponent data. We describe statistical ways of estimating these mixing matrices. By taking advantage of the redundancy of seismic data, we here present a way to simultaneously reconstruct the mixing matrices, the upgoing and downgoing wavefields by essentially using the statistical methods. The attractive features of the statistical wavefield methods are that they are independent of the data dimension (i.e., they are applicable to 2D and 3D data without any modification of the computer code and without a sampling or interpolation requirement) and that they work for aliased data as well as for nonaliased data, and even for nonuniform sampled data. The only assumptions here are that (1) the mixing matrix is invertible and (2) the number of datapoints is large enough for statistical applications.