In a pilot inner-city survey, nine 1-year-old infants with nonorganic failure to thrive (NOFT) and pairwise matched controls from the same deprived inner-city area were studied at home. A multimethod approach to the study of infant behavioral style was adopted. A consistent pattern of NOFT infants' behaviors in mothers' descriptions, in observation of play behavior, and in interaction with the examiner during standard testing emerged. NOFT infants were found to be more fussy, demanding, and unsociable. They were also less task-oriented and persistent, and their mothers expressed more negative emotions during play interaction. Mental development was significantly delayed in NOFT infants. The findings emphasize the importance of behavioral contributions from both infant and mother to the relationship problems characteristic of NOFT.