Although 5 biologic therapies have Food and Drug Administration (FDA)-approved indications for difficult-to-control asthma, the clinical trials that proved the efficacy and safety of these biologics were similar in their inclusion criteria, study protocols, and measured outcomes. Initial trial results are now being reanalyzed and reinterpreted in subsets of patients with asthma that demonstrate enhanced responses. As a result, keeping up with the growing body of literature surrounding asthma biologic therapy has become increasingly difficult. This review summarizes and compares trial designs, patient cohorts, and study results of the major trials involving these therapies. Because of variations in inclusion criteria and natural variations in enrolled cohorts, the baseline clinical traits and severity of study populations in asthma biologic trials have differed significantly. For example, baseline annualized exacerbation rates in the year before enrollment and blood eosinophilia, which are both strong predictors of a biologic's success, differed strongly among populations. Early omalizumab efficacy trials did not stratify subjects by blood eosinophils or include patients taking long-acting beta agonists or oral steroids but showed relative reductions in exacerbation rates comparable to those of the newer asthma biologics among less severe cohorts. If a care provider's aim is to reduce clinically significant exacerbations in a patient with peripheral blood eosinophilia, it is our opinion that dupilumab, mepolizumab, and reslizumab have the strongest supporting data. Mepolizumab has also demonstrated an ability to reduce emergency department visits and hospitalizations. If the goal is to improve lung function, dupilumab therapy has demonstrated the largest numeric improvements in prebronchodilator forced expiratory volume in 1 second (FEV 1) % predicted compared with placebo, with consistent results across all phase II and phase III trials, including its steroid-sparing trial (QUEST LIBERTY VENTURE). Benralizumab also demonstrated improvements in lung function in 2 phase III trials (SIROCCO, CALIMA) and its long-term safety trial (BORA). If the objective is to reduce daily oral steroids, benralizumab and dupilumab have the strongest supporting data, with roughly 50% of subjects in both trials demonstrating an ability to stop steroids altogether. Of note, a strong difference was seen across studies in the ability to reduce steroids among the placebo groups, which makes comparisons between these 3 steroid-sparing trials challenging.