pasos is a parental allocation program designed to identify collected parents based on individual multilocus genotypes while detecting missing parents when a proportion of them have not been collected. It makes use of restricted error tolerance in order to distinguish between a partially incorrect genotype from a false parent's genotype. pasos also introduces the technique of sequence allocation allowing the user to obtain estimates of the proportion of missing parents and of allocation correctness. The pasos interface is very similar to the one found in papa, its closed system counterpart (Duchesne et al. 2002). A help file thoroughly describes all technical terms such as error modelling, parameters and procedures. pasos can be downloaded free of charge from: http://www.bio.ulaval.ca/louisbernatchez/.