The purpose of this study was to extend work seeking to improve research definitions of chronic maltreatment by contrasting a definition based on patterns of CPS reports across childhood developmental stages to a previously used definition based upon duration of the period including reports, using teacher-estimated peer relations to represent an extrafamilial outcome domain of social adaptation. The sample includes 387 children who are participating in a multi-site longitudinal study and had been reported for abuse or neglect to CPS between birth and age 8. CPS records from this time period provided the basis of two chronicity constructs: 1) an ordinal categories (OC) definition based upon four Eriksonian stages, and 2) a durational definition (time between first and last reports). Block-wise regression analyses were conducted to examine the relative degree to which the two chronicity definitions contributed to prediction of teacher-estimated peer relations at the age 8 interview. Chronicity characterized with reference to developmental stages significantly predicted troubled peer relations, with child age, sex, and minority status, family income, geographic location, and time of first report taken into account. The effect was pronounced with regard to aggressive peer relations. Duration of maltreatment reports also predicted aggressive peer relations, but significantly less so than did the OC definition. The findings support the view that maltreatment chronicity is usefully defined by taking children's development into consideration to characterize patterns of maltreatment across developmental stages. Practice and research implications are suggested. Tables, figure, and references (Published Abstract)