The most important benefit of tocolysis is a 48-hour prolongation of gestational age in order to administer corticosteroids to reduce perinatal mortality and morbidity as well as, if necessary to gain time for "in utero" transfer to a tertiary centre with neonatal facilities. The tocolytic agents used in clinical practice can be grouped into six classes, namely: calcium channel blockers, betamimetics, magnesium sulfate, cyclooxygenase inhibitors, oxytocin receptor antagonists and nitric oxide donors. The use of them should be individualized and based on tocolytic effectiveness, safety gestational age as well as maternal, fetal and neonatal outcomes. Data from clinical trials suggests that nifedipine appears to be the drug of first choice in the management of preterm labor.