Behavioral and emotional problems are highly prevalent in early childhood and represent an important focus of practice for clinical child and pediatric psychologists. Although psychological or psychiatric disorders are not typically diagnosed in children under the age of 2 years, recent research has demonstrated the appropriateness of assessing behavioral and emotional problems during the first 2 years of life (defined throughout as "infancy"). The current paper provides a systematic review of assessment procedures used to identify behavioral and emotional problems during infancy. Existing assessment procedures for infants take the form of parent- or caregiver-report questionnaires, observational coding procedures, and diagnostic classification systems. The questionnaires and observational coding procedures both had substantial psychometric evidence for use with infants, although observational coding may have limited utility in clinical practice. The classification systems have less empirical support for use with infants, and further research is necessary to demonstrate the appropriateness of these procedures with infants. Utilizing the reviewed procedures to assess behavioral and emotional problems in infants can have a substantial impact in research and practice settings, and further research is needed to determine the usefulness of these procedures in developing, testing, and implementing preventive and early intervention programs for infants and their families.