The objective of this review was to compare the effects of prophylactic doses of nedocromil sodium (NCS) and sodium cromoglycate (SCG) on postexercise lung function, in persons diagnosed with exercise-induced bronchoconstriction. Randomized controlled trials were identified from the Cochrane Airways Review Group Asthma Register, plus hand searching for trials in journals, bibliographies of relevant studies and review articles. Randomized controlled trials comparing NCS to SCG in prophylactic treatment of exercise-induced bronchoconstriction were eligible. Studies were pooled using odds ratios (OR) for dichotomous outcomes or weighted mean differences (WMD) with 95% confidence intervals (95% CI) for continuous outcomes. No significant differences were noted between NCS and SCG with respect to the maximum per cent decrease in forced expiratory volume in one second (WMD=-0.88; 95% CI -4.50-2.74), complete protection (OR=0.95; 95% CI 0.50-1.81), clinical protection (OR=0.71; 95% CI 0.36-1.39), unpleasant taste (OR=6.85; 95% CI 0.77-60.73), or sore throat (OR=3.46; 95% CI 0.32-37.48). Subgroup analyses based on age, dosages of medications and timing of exercise postinhalation were consistent with the overall pooled analyses. No significant differences were evident between the effects of nedocromil sodium and sodium cromoglycate during the immediate postexercise period in adults and children with exercise-induced bronchoconstriction, with regards to maximum per cent decrease in forced expiratory volume in one second, complete protection, or clinical protection. Side-effect profiles were similar.