The influences of maternal characteristics, infant characteristics, and paternal support on maternal positive involvement and developmental stimulation were examined over time in 59 mothers and their medically fragile infants using an ecological framework. Higher maternal education was associated with greater maternal positive involvement. More maternal depressive symptoms, more infant technological dependence, and lower birthweights were associated with less maternal positive involvement at 6 months but greater involvement at 12 months. Higher paternal helpfulness facilitated positive involvement in mothers with low depressive symptoms but not in those with elevated symptoms. Higher maternal education and more depressive symptoms were associated with more developmental stimulation. Thus, maternal interactive behaviors are affected by maternal, infant, and environment factors, and these effects change over time.