Allergen immunotherapy is effective in patients with allergic rhinitis (AR) and, unlike antiallergic drugs, has been shown to modify the underlying cause of the disease, with proved long-term benefits. Subcutaneous immunotherapy (SCIT) has been the gold standard, whereas sublingual immunotherapy (SLIT) has emerged as an effective and safe alternative. Previous Cochrane systematic reviews and meta-analyses have confirmed that both SLIT and SCIT are effective in patients with seasonal AR, whereas evidence for their efficacy in patients with perennial disease has been less convincing. Recent large, adequately powered trials have demonstrated reductions in both symptoms and use of rescue medication in patients with seasonal and those with perennial AR. Here we appraise evidence for SCIT versus SLIT based on indirect evidence from Cochrane reviews and recent well-powered double-blind, randomized controlled trials versus placebo and the limited direct evidence available from randomized blind head-to-head comparisons. At present, based on an overall balance of efficacy and side effects, the patient is in equipoise. Pending definitive comparative trials, choice might be determined largely by the local availability of SCIT and SLIT products of proved value and personal (patient) preference.