the effect of crop rotation on the incidence of common bean “amachamiento” was evaluated in the “brunca” region in costa rica during 2009 complemented by a field observation during 2010. the incidence of “amachamiento” in 2009 was quantified in vegetative (v3 or v4), flowering (r6) and pod-production (r8) plant growth stages, in bean commercial fields rotating with previous rice, corn, hot-pepper, pumpkin or bean. four micro-plots (10 m2) were established in each field; to score “amachamiento” incidence, data were subjected to angular transformation and statistical means among treatments were separated by anova. the 2010 field observation was developed in a farm growing common beans on soils previously planted with either ginger, taro or corn. in 2009, during the r8 growth stage a minimum incidence was detected in the hotpepper- bean rotation (4%), intermediate levels in the pumpkin-bean (15%) and rice-bean rotation (29%), and high incidence in both bean-bean (62%) and corn-bean (64%) rotations. in the 2010 field observations, during the flowering stage “amachamiento” incidence was 4% in the ginger-bean rotation and 5% in the taro-bean one, significantly lower than in the corn-bean rotation (25%). based on these results, crop rotations such as hot-pepper, ginger, taro or pumpkin preceding common bean can reduce both “amachamiento” incidence and, consequently, yield losses.