We performed an observational study to determine whether allergen-specific sublingual immunotherapy (SLIT) is as effective as allergen-specific subcutaneous injection immunotherapy (SCIT). Our study population was comprised of 66 patients who had been taking SLIT. Of this group, 36 patients had switched to SLIT after having been treated with SCIT (group I), while the remaining 30 patients had received SLIT only (group II). A questionnaire was used to evaluate the results of treatment. In group I, 33 patients (92%) gave SLIT a favorable rating; 27 of these patients (75%) said it was just as effective as SCIT, and 6 (17%) said it was actually superior (the remaining 3 patients [8%] said that SCIT was better). In group II, 27 of 30 patients (90%) said they had attained symptom relief with SLIT; 21 (70%) said that the relief had been very significant. Overall, 60 of the 66 patients (91%) expressed various degrees of satisfaction with SLIT. We believe that our SLIT protocol, which is based on established guidelines for SCIT administration, is an effective, safe, well-tolerated, and easy-to-use regimen. Future prospective studies of larger groups are clearly indicated.