For many years, appropriate relevance has not been given for pain in newborn infants, but research brought to light this important subject in neonatal medicine. Pain scores have been organized in scales and validated to be used in clinical practice. Currently, there are several scales based on different pain indicators. These scales should be used according to different circumstances. With the purpose of helping health professionals, a systematic review of neonatal pain scales based on gestational age, duration of painful episode and type of pain indicator was carried out. Data concerning validation of the scales were also analyzed and two scales for use in clinical practice or in research are suggested.