Abstract : We have studied the negative secondary ion emission from solid organic targets bombarded by molecular ions and cluster ions. As an example we present here the results obtained with the compound phenylalanine. We have used organic projectiles of mass 73 [Si (CH3)+], 147[Si(CH3)3 OSi(CH3)2+], 300 [molecular ion of coronene C24H12]+, 598 [coronene dimer 2(M-H)]+, and atomic and polyatomic ions of mass 133 [Cs]+, 393 [Cs2I]+, 653 [Cs3I2]+. These primary ions have been produced in the bombardment of targets of coronene and CsI by fission fragment from a 252Cf source. They were accelerated and focussed on the sample target. Sophisticated time of flight measurements of the primary and secondary ions have been performed with a special data acquisition system. All the time of flight mass spectra were recorded at one. The secondary molecular ion yield of the phenilalanine (M-H)- = 164 has been studied as a function of the energy of impact and of the mass of the projectile. A large enhancement of the yield with the mass and the energy is observed.