This article has attempted to establish the importance of considering behavioral disturbances in infancy and early childhood as disturbances of the parent-child relationship. When the psychologic and mental mechanisms of the individual infant are too immature to sustain disturbed behavior across several settings and when the behavioral disturbance seems to be specific to a particular relationship, it is more appropriate to diagnose the pathology as being in the relationship. The article has offered a diagnostic framework of relationship pathology that spans the spectrum from normal variation (relationship perturbation) to relationship behaviors that are at risk of becoming a disorder (relationship disturbance) to significant relationship disorders that most likely require a professional intervention. A multiaxial assessment protocol is recommended that evaluates primary relationships (Axis I), parent-infant interaction styles (Axis II), the parent and infant as individuals (Axis III), and more distal contextual factors that affect the relationship (Axis IV). Sleep disturbances in infancy have been used as an example to demonstrate the spectrum of relationship pathology. Additional research is needed to develop more precise, age-relevant cut points for the spectrum of relationship pathology for sleep problems and for other parent-infant relationship disturbances in the areas of feeding, excessive crying, and limit setting or tantrums. More research is also needed to define better when and how relationship pathology becomes transformed into individual pathology and how early intervention may alter the course of this trajectory.