The reaction geometry of selected species can be controlled by using polarized light even in bulk experiments. One reactant A is generated in a photodissociation process. Its spatial distribution is completely described by the anisotropy parameter beta. The other molecular reactant B is excited in a specific rovibrational state. Its spatial distribution is given by the j- and branch-dependent alignment parameter A(0)((2)). The unnormalized probability of an attack of A on B under an angle gamma is then given by the simple expression P(gamma) proportional to [1 + 1/5 beta A(0)((2))P-2(cos gamma) P-2(cos delta)], where delta is the angle between the (E) over right arrow-vectors of the dissociating and of the exciting laser beams. P-2(x) represents the second Legendre polynom. We have studied the reaction of X + HCN --> HX + CN with X = H, Cl. The attacking H atom is generated in the photodissociation of CH3SH at 266 nm, and the chlorine atom is formed in the photolysis of Cl-2 at 355 nm. In both cases the beta-parameter is close to -1. In order to align the HCN partner reactant, the first and third vibrational overtone of the CH stretch vibration was excited via the R and P branches. The nascent CN(v = 0) product molecules were observed by laser induced fluorescence(LIF). The experimental results prove a preferred linear reaction geometry, i.e. an end-on attack of the X atom on the terminating hydrogen atom of the HCN reactant. However, the angle of acceptance is higher for the Cl + HCN reaction than for the H + HCN one.