Side effects of antidepressants can be predicted by receptor selectivity and site of action. Although the selective serotonin reuptake inhibitors (SSRIs) have better overall safety and tolerability than older antidepressants, broad-based experience with SSRIs has shown the frequency and type of side effects to be increased relative to clinical trial data. The author explores the reasons for the different profiles and discusses adverse effects, especially sexual dysfunction, weight gain, and sleep disturbance, the most troubling adverse events seen during long-term SSRI therapy. The informed management of these side effects by primary care practitioners supports successful treatment of depression.