IN ORDER TO STUDY RELATIVE FITNESS OF RESISTANT AND SUSCEPTIBLE LOLIUM RIGIDUM BIOTYPES TO ACCASE INHIBITING HERBICIDES, IN DROUGHT STRESS CONDITIONS, AN EXPERIMENT WAS CARRIED OUT BY FACTORIAL BASED ON COMPLETELY RANDOMIZED DESIGN WITH THREE REPLICATIONS. TREATMENTS CONSISTED OF MATRIC POTENTIAL FIVE LEVELS (0, -3, -6, -9, -12, -15 BARS) AND THREE RESISTANT, SEMI RESISTANT AND SUSCEPTIBLE LOLIUM RIGIDUM BIOTYPES TO ACCASE INHIBITING HERBICIDES. POLYETHYLENE GLYCOL WAS USED TO PREPARE DIFFERENT DROUGHT LEVELS. RESULTS REVEALED THAT SUSCEPTIBLE BIOTYPE HAD HIGHEST GERMINATION RATE. AMONG DIFFERENT MATRIC POTENTIAL, CONTROL AND -15 BAR POTENTIAL HAD THE HIGHEST AND LOWEST GERMINATION RATE, RESPECTIVELY. THE DIFFERENCE AMONG -3, -6, -9 AND -12 BARS POTENTIALS WAS NOT SIGNIFICANT.