BACKGROUND: Hammock positioning is now frequently used with preterm infants admitted to ICUs. However, few studies have investigated the extent to which hammock positioning reduces pain and improves the sleep-wakefulness state compared with traditional positioning. METHODS: Twenty-six clinically stable newborns with gestational ages from 30 to 37 weeks who were breathing spontaneously were randomly assigned to 2 groups: a hammock-positioning group (n ‫؍‬ 13), in which newborns were placed in hammocks in the lateral position, and a traditional-positioning group (n ‫؍‬ 13), in which they were kept nested, also in the lateral position. The following variables were evaluated at the beginning and the end of the treatment: pain (with the Premature Infant Pain Profile, and Neonatal Facial Coding System), sleep-wakefulness state (with the Brazelton Neonatal Behavioral Assessment Scale), heart rate, breathing frequency, and peripheral S pO 2. RESULTS: The subjects in the hammock-positioning group showed an improvement in pain compared with the traditional-positioning group(Premature Infant Pain Profile score, 2.62 ؎ 1.89 vs 2.31 ؎ 1.97, ⌬P ‫؍‬ .008) and sleep-wakefulness state score (2.08 ؎ 0.64 vs 1.23 ؎ 0.44, ⌬ P < .001), reduced heart rate (151.69 ؎ 5.44 vs 142.77 ؎ 5.18 beats/min, ⌬ P < .001), breathing frequency (52.31 ؎ 4.05 vs 50.23 ؎ 2.55 beats/min, ⌬ P ‫؍‬ .024), and increased peripheral S pO 2 (94.69 ؎ 2.14 vs 98.00 ؎ 1.22%, ⌬ P < .001). CONCLUSIONS: Hammock positioning was an effective treatment option to reduce pain and improve sleep-wakefulness state. It also helped to reduce heart rate and breathing frequency, and to increase peripheral S pO 2 , which made it a treatment option for preterm infants.