I discussed, in this chapter, the possibilities and limitations of clinical diagnosis for Asperger syndrome (AS) in infancy and early childhood. For early diagnosis or simply noticing the possibility of AS, clinicians should be sensitive to the auxiliary conditions of AS such as motor dysfunction and sensory/sleep disturbances during the early stage of life, as well as the incipient representations of the main AS symptoms in the diagnostic criteria, such as lack of reciprocal social interaction or joint attention. Future prospective study with large cohort, or creation of the new methods for cognitive evaluation which is applicable to infants and toddlers, would be profitable in order to establish the sensitive tool for AS diagnosis in early infancy, while the idea would be expected undoubtedly elusive.