Plants, for hundreds of millions of years, have been evolving defensive strategies to protect themselves against herbivores and pathogens. Jasmonates are signaling molecules that play a key role in this defense process, although they also act in regulation of metabolic processes and reproduction. Phenylalanine ammonia lyase (PAL, EC.4.3.1.1.) is the first enzyme of the phenyl propanoid pathway, and is commonly activated as part of plant defensive responses to several stresses. In this work we investigated the effects of wounding and methyl jasmonate (MeJa) on the protein pattern of Ricinus communis L. leaves and the effects of these treatments on PAL activity. Castor bean seeds (cultivar IAC-80) were germinated in plastic pots containing a mixture of soil and vermiculite under controlled conditions in a greenhouse. Plants at the three-leaf-stage (14 days) were sprayed with 1 mM solution of methyl jasmonate in 0.1% triton X-100 or wounding with a surgical pincers. Control plants did not receive any treatment. At specific intervals after methyl jasmonate treatment and wounding, primary leaves of each plant were harvested, grounded with pestle and mortar, and proteins were extracted with Tris-HCl buffer (50 mM pH 8,0) with PVPP 2%, 1 mM PMSF and 10 mM EDTA. The mixture was centrifuged at 14,000 × g for 20 min and the supernatant was analyzed by SDS-PAGE 15% and tricine-SDS-PAGE. PAL activity was determined by mixing 100 µl of enzyme preparation with 100 mM Tris–HCl buffer (pH 8.5) containing 12 mM L-phenylalanine in a final volume of 1 ml. The mixture was incubated at 40 °C for 60 min. The reaction was stopped by the addition 50 µl of 5 N HCl. The product (transcinnamic acid) was detected and quantified by measuring absorbance at 290 nm against a blank. Ours results showed low molecular mass induced proteins with 6,5; 5,5; 4,9 and 4,3 kDa after wounding treatment (72h). We observed the reduction of both Rubisco subunits (small and large) and the reduction of a protein with 22 kDa in plants treated with MeJa. This treatment also promoted the induction of two proteins (62 and 28,5 kDa). Wounding and MeJa increased the PAL activity, however this increase was more pronounced in the plants treated with MeJa.