Background Inotropes are widely used in preterm infants to treat systemic hypotension. The most commonly used drugs are dopamine and dobutamine. These agents have different modes of action which may result in different haemodynamic effects. Objectives To compare the effectiveness and safety of dopamine and dobutamine in the treatment of systemic hypotension in preterm infants. Search strategy Searches of electronic and other databases were performed including MEDLINE (1966-2002), EMBASE (1988-2002), Science Citation Index (1981-2002), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2003). Previous reviews were searched for references to relevant trials and leading authors in the field were contacted for information about other published and unpublished studies. Selection criteria Randomised controlled trials where short and/or long term effects of treatment with dopamine and dobutamine for the treatment of systemic arterial hypotension were compared were selected for this review. Trials studying newborn infants born before 37 completed weeks gestation and less than 28 days of age were eligible for inclusion. Systemic arterial hypotension was not defined specifically, but accepted as defined in individual studies. Studies were not limited by birthweight, lower gestational age threshold or by route or duration of administration of inotropic agents. Study quality and eligibility were assessed independently by each reviewer. Data collection and analysis Data extraction was performed independently by each reviewer, with differences being resolved by discussion. The following outcomes were determined: mortality in the neonatal period, long term neurodevelopmental outcome, radiological evidence of severe neurological injury, short term haemodynamic changes and incidence of adverse effects. The effect of interventions was expressed either as Relative Risk (RR), Risk Difference (RD) or as Weighted Mean Difference (WMD) with their 95% Confidence Interval (CI). Main results Five trials met the pre-defined criteria for inclusion in this review. There was no evidence of a significant difference between dopamine and dobutamine in terms of neonatal mortality (RD 0.02 95% CI -0.12 to 0.16), incidence of periventricular leukomalacia (RD -0.08, 95% CI -0.19 to 0.04), or severe periventricular haemorrhage (RD -0.02, 95% CI -0.13 to 0.09). Dopamine was more successful than dobutamine in treating systemic hypotension, with fewer infants having treatment failure (RD -0.23, 95% CI -0.34 to -0.13; NNT = 4.4, 95% CI 2.9 to 7.7). Treatment with dobutamine was associated with a significantly greater increase in left ventricular output in the single study reporting that outcome. There was no evidence of a significant difference between the two agents with respect to the incidence of tachycardia (RD -0.06, 95% CI -0.25 to 0.14). None of the studies reported the incidence of adverse long term neurodevelopmental outcome. Authors' conclusions Dopamine is more effective than dobutamine in the short term treatment of systemic hypotension in preterm infants. There was no evidence of an effect on the incidence of adverse neuroradiological sequelae (severe periventricular haemorrhage and/or periventricular leucomalacia), or on the incidence of tachycardia. However, in the absence of data confirming long term benefit and safety of dopamine compared to dobutamine, no firm recommendations can be made regarding the choice of drug to treat hypotension.