Root-knot nematodes are the most economically important nematodes on a worldwide basis. Prediction of the crop loss that a certain population density of nematode may cause is of importance to decide whether to cultivate a plant or not. It is also of use for choosing the most suitable managing strategies. A pot experiment was devised to determine the damage potential of an Iranian population of Meloidogyne javanica on pepper (cv. California Wonder). Two leaves seedlings were planted in 3 kg pots contain different inoculum level of 0, 0. 125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256 and 512 eggs and juveniles g -1 sandy loam soil. Shoot weight, yield and nematode reproduction rate were negatively correlated with initial inoculum level of nematode while the root response was variable. Seinhorst's model fitted the data of yield and shoot weight and a tolerance limit of 0.5 and 0.28 eggs and juveniles g -1 soil was respectively estimated. The minimum relative yield and shoot weight was 0.16 and 0.3, respectively. The damage threshold was estimated of 1.8 eggs and juveniles g -1 soil by Seinhorst's model. The maximum multiplication rate and the equilibrium density of M. Javanica were estimated as 708.31 and 159.65 (eggs and juveniles g -1 soil), respectively.