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within the family may change the quality of the mother-child relationship (Belsky, 1981; Hops et al., 1987). A number of plausible explanations for the lack of inclusion of fathers in clinical research have been offered. From a theoretical perspective, ignoring fathers' possible influence tends to focus the "blame" for children's problems on mothers (Caplan & Hall-McCorquodale, 1985; Downey & Coyne, 1991; Phares, 1992), thereby maintaining a sexist bias based on outmoded concepts of parental roles (Phares, 1992, 1996a). Research over the past two decades has shown that despite the lesser role fathers may play, at least in terms of proportional involvement, they can and do make significant contributions to the child's normal development that in some respects are very similar to the effects shown by mothers (Lamb, Pleck, & Levine; 1985; Parke, Maddonald, Beitel, & Bhavnagri, 1988). Moreover, a review of the studies with both referred and non-referred samples of fathers and children indicates that there is a substantial association between paternal factors and child and adolescent maladjustment (Phares & Compas, 1992).
Another explanation for excluding fathers in research relates to the assumption that many children, particularly those who are clinic-referred, do not have contact with their biological father (Phares & Lum, 1997). Based on the U.S. Census data, Roberts (1993) documented that 61% of children under 18 years old in the United States live with both of their biological parents. A total of 11% of children live with one biological parent and a stepparent, 24% live with their single (never married, separated, divorced, or widowed) mother, and 4% live with their single father. These figures differ according to race and ethnicity, with the most striking difference showing that 26% of African American children