Purpose: This study was conducted to identify behavioral items for Korean infants under 24months by naturalistic observation. These items will be the basis for developmental scale for Korean infants. Method: Data were collected by observing and interviewing fifty one infants and their mothers during the period from November 15 to December 14, 2003. Raw data in descriptive form were obtained by unstructured naturalistic observation, and were reformed to behavioral items through discussion with professors in pediatric nursing and experienced nurses in child care department. Also, behavioral items were classified into five developmental areas. Result: Total number of behavioral items was two hundreds and thirty eight. 52 items for motor development, 66 items for personal-social, 40 items for hearing and speech, 41 items for eye-hand coordination, and 39 items for performance. Conclusion: This is meaningful that fundamental items for Korean developmental scale for infants were identified by observing behaviors of Korean infants. On the basis of these items, average age will be calculated for passing each item by testing Korean infants. We hope to develop Korean infant developmental scale as a final outcome in the future research.