Objective: To examine the prevalence of encopresis/enuresis, relationship between maternal hostility and encopresis, parent-child concordance of reporting encopresis/enuresis, and familial aggregation of enuresis in subjects with a prepubertal and early adolescent bipolar-I disorder phenotype (PEA-BP), attention-deficit/hyperactivity disorder (ADHD), and healthy controls (HC). Method: There were 268 consecutively ascertained subjects (93 PEA-BP, 81 ADHD, and 94 HC). PEA-BP was defined as DSM-IV BP-I (manic or mixed phase) with elation and/or grandiosity. The WASH-U-KSADS and Psychosocial Schedule for School-Age Children-Revised were administered to parents about their children and separately to children about themselves. Results: Encopresis was more prevalent in PEA-BP versus HC subjects (15.1% versus 3.2%, [chi square] = 6.4, p = .012). Enuresis was more common in PEA-BP versus HC (21.5% versus 6.4%, [chi square] = 7.8, p = .005) and ADHD versus HC (22.2% versus 6.4%, [chi square] = 6.1, p = .014) subjects. All enuresis onset in subjects not receiving lithium. Most encopresis (81.8%) and enuresis (75.0%) onset before mania. Familial aggregation of enuresis was more frequent in enuretics than nonenuretics (47.7% versus 5.4%, [chi square] = 41.2, p [is less than] .0001). Maternal hostility was more prevalent in encopretic versus nonencopretic subjects (91.7% versus 55.6%, [chi square] = 8.3, p = .004). Parent-child concordance on reporting encopresis and enuresis was poor to fair. Conclusions: Children with PEA-BP need to be evaluated for encopresis, enuresis, and mother-child relationships.