We present a new algorithm for the computation of resultants associated with multihomogeneous (and, in particular, homogeneous) polynomial equation systems using straight-line programs. Its complexity is polynomial in the number of coefficients of the input system and the degree of the resultant computed. Key words: Sparse resultant, multihomogeneous system, Poisson-type product formula, symbolic Newton’s algorithm. MSC 2000: Primary: 14Q20, Secondary: 68W30.