BACKGROUND:Timothy grass sublingual immunotherapy (SLIT) tablets are indicated for children with allergic rhinitis with or without conjunctivitis. OBJECTIVE:To use pooled analyses to assess the short- and long-term tolerability and safety of timothy grass SLIT-tablet in children. METHODS:Data from 9 double-blinded, randomized European or North American trials that included children with allergic rhinitis with or without conjunctivitis treated up to 3 years with once-daily timothy grass SLIT-tablet or placebo were pooled. RESULTS:In all, 1818 (timothy grass SLIT-tablet, n = 923; placebo, n = 895) subjects were included in the analysis. The frequency of treatment-emergent adverse events (AEs) was 86% in the SLIT-tablet group and 83% in the placebo group, and the frequency of treatment-related AEs (TRAEs) was 59% and 23%, respectively. Most (98%) TRAEs were mild to moderate in severity. The 2 most common TRAEs with SLIT-tablet were oral pruritus (33%) and throat irritation (19%), which had a median onset of 1 day and recurrence of 14.5 and 5 days, respectively. In all, 8% of subjects in the SLIT-tablet group and 2% in the placebo group discontinued because of AEs. There were 7 serious AEs assessed as related to SLIT-tablet, 1 systemic allergic reaction (severe with a drop in blood pressure), 3 epinephrine administrations, no eosinophilic esophagitis events, and no serious airway obstructions. The safety profile was similar in subjects across geographic regions and with and without asthma. CONCLUSIONS:Pooled data indicate that short- and long-term timothy grass SLIT-tablet is well tolerated in children, regardless of geographic region. AEs were generally local, mild, and transient allergic reactions.