Three populations of Pratylenchus spp. were collected from coffee roots in three different ecological zones in Guatemala, reared on carrot discs, and characterised by morpho-biometry, biology and pathogenicity studies. Biometric characters showed that these populations belong to the "P. coffeae-P. loosi complex" (males present, two lip annules, stylet : 13.6-16.0 microm, V : 73.6-86.8%, tail conoid with various tip shape); according to SEM observations, two populations belong to the group 1 of Corbett and Clark (1983) whilst the third belongs to group 2. These three populations seems to be obligatory amphimictic : i) no multiplication occurred for single juvenile inoculations on carrot discs (n = 20); ii) multiplication was observed in 33% and 100% of two juvenile (n = 20) and ten-juvenile inoculations (n = 2 to 6 depending on the population) respectively. Furthermore, cross-breeding experiments with these populations were all unsuccessful, indicating the existence of reproductive barriers. The three populations exhibited significant differences in reproductive fitness in carrot discs but they all had a maximal multiplication rate at 27°C. In parallel their pathogenicity on coffee seedlings was also significantly different but not correlated with their respective reproductive fitness on carrot discs.