Results of a provenance/progeny test of Alnus acuminata in Costa Rica are presented. The treatments consisted of 45 open-pollinated families of one Guatemalan and 4 Costa Rican provenances. At 34 months, the Guatemalan provenance was significantly inferior in height and diameter growth rate, basal forking, stem lean and stem straightness. In addition, it was heavily attacked by the bark beetle Scolytodes alni, whilst the Costa Rican provenances were not attacked. There was little evidence for genetic differentiation between the Costa Rican provenances. There was no evidence of provenance related variation in the traits basal sweep and branch angle, nor in growth traits before age 34 months (except height increment between months 22 and 34). The family analysis, from which the Guatemalan families were omitted, revealed significant additive genetic variation in all the form and growth traits examined, except stem lean and non-basal forking. Estimates of heritability and additive genetic coefficient of variation for growth, stem straightness and branching traits were within the ranges typically found in forest trees. In spite of the presence of some adverse genetic correlations between height growth and form traits, in general the estimated values of the genetic parameters confirmed the potential for genetic improvement of Alnus acuminata in Costa Rica.