The present study objective was to determine some of the main life history characteristics of the chiochio, Psectrogaster rutiloides, a heavily fished, yet poorly studied species of the Peruvian Amazon. Over an annual cycle between 2006 and 2007 a monthly sampling of P. rutiloides on the Iquitos market provided a total of 2973 individuals. The species reproduces during the rainy season, during the first part of the flooding period. First sexual maturity is reached at about 2 years of age and 95 mm standard length (SL) for both males and females. Batch fecundity was related to fish size and varied from 59 800 to 149 100 oocytes, with oocytes diameters of 1.34 ± 0.11 mm, valid for females of 141 and 152 mm SL and of 102.9 and 149.6 g body mass, respectively. Females grew faster than males in every age class, a difference gradually increasing from 7% at age one to 10% at age nine, which corresponded to the oldest individuals sampled. Estimated mortality parameters and exploitation rates suggested over‐exploitation of the species in the Loreto region.