In existing studies, researchers suggest that children’s rank order in effortful control tends to remain moderately stable during early childhood (Carlson, Mandell, & Williams, 2004; Kochanska & Knaack, 2003). Children’s effortful control also has been moder- ately consistent as children transition from preschool to middle childhood (Eisenberg, Sadovsky, et al., 2005; Eisenberg et al., 2003; Murphy, Eisenberg, Fabes, Shepard, & Guthrie, 1999; Ol- son, Schilling, & Bates, 1999). Additionally, children have less difficulty controlling their behavior and attention as they grow older (Gerstadt, Hong, & Diamond, 1994; Jacques & Zelazo, 2001; Olson et al., 1999), with large improvements occurring between ages 2 and 3 years (Carlson et al., 2004; Kochanska, Murray, & Harlan, 2000). Growth in behavioral and attentional regulation may slow as children grow older, with less improvement occurring after age 4 years (Jones, Rothbart, & Posner, 2003; Murphy et al., 1999).These findings have been noted in studies of children from a range of socioeconomic and racial/ethnic backgrounds. Still, we know relatively little about whether these patterns would hold among large groups of ethnic minority children. Studies that are focused on the development of effortful control among those low-income children, who are disproportionately African Ameri- can and Latino, would add to the generalizability of existing research, would answer calls for tests of normative models among ethnic minority children (Garcia Coll et al., 1996), and would address the pressing need for the study of developmental phenom- ena among Latino children (Flores, Cicchetti, & Rogosch, 2005; Flores et al., 2002; Mistry, Vandewater, Huston, & McLoyd, 2002), who are among one of the fastest growing immigrant groups in the United States (Flores et al., 2002).