BACKGROUND Mother-infant separation postbirth is common in Western culture. Early skin-to-skin contact (SSC) begins ideally at birth and involves placing the naked baby, covered across the back with a warm blanket, prone on the mother's bare chest. According to mammalian neuroscience, the intimate contact inherent in this place (habitat) evokes neurobehaviors ensuring fulfillment of basic biological needs. This time may represent a psychophysiologically 'sensitive period' for programming future behavior. OBJECTIVE To assess the effects of early SSC on breastfeeding, behavior, and physiological adaptation in healthy mother-newborn dyads. METHODS Cochrane Pregnancy and Childbirth Group's and Neonatal Group's Trials Registers (August 2006), Cochrane Central Register of Controlled Trials (The Cochrane Library 2006, Issue 2), MEDLINE (1976 to 2006). METHODS Randomized and quasi-randomized clinical trials comparing early SSC with usual hospital care. METHODS We independently assessed trial quality and extracted data. Study authors were contacted for additional information. RESULTS Thirty studies involving 1925 participants (mother-infant dyads), were included. Data from more than two trials were available for only 8-of-64 outcome measures. We found statistically significant and positive effects of early SSC on breastfeeding at one to four months postbirth (10 trials; 552 participants) (odds ratio (OR) 1.82, 95% confidence interval (CI) 1.08 to 3.07), and breastfeeding duration (seven trials; 324 participants) (weighted mean difference (WMD) 42.55, 95% CI -1.69 to 86.79). Trends were found for improved summary scores for maternal affectionate love/touch during observed breastfeeding (four trials; 314 participants) (standardized mean difference (SMD) 0.52, 95% CI 0.07 to 0.98) and maternal attachment behavior (six trials; 396 participants) (SMD 0.52, 95% CI 0.31 to 0.72) with early SSC. SSC infants cried for a shorter length of time (one trial; 44 participants) (WMD -8.01, 95% CI -8.98 to -7.04). Late preterm infants had better cardio-respiratory stability with early SSC (one trial; 35 participants) (WMD 2.88, 95% CI 0.53 to 5.23). No adverse effects were found. CONCLUSIONS Limitations included methodological quality, variations in intervention implementation, and outcome variability. The intervention may benefit breastfeeding outcomes, early mother-infant attachment, infant crying and cardio-respiratory stability, and has no apparent short or long-term negative effects. Further investigation is recommended. To facilitate meta-analysis, future research should be done using outcome measures consistent with those in the studies included here. Published reports should clearly indicate if the intervention was SSC and include means, standard deviations, exact probability values, and data to measure intervention dose.