  We present a scheme to produce an entangled four-photon W-state by using
linear optical elements. The symmetrical setup of linear optical elements
consists of four beam splitters, four polarization beam splitters and four
mirrors. A photon EPR-pair and two single photons are required as the input
modes. The projection on the W-state can be made by a four-photon coincidence
measurement. Further, we show that by means of a horizontally oriented
polarizer in front of one detector the W-state of three photons can be
generated.
