To evaluate the feasibility and safety of initially dispatching only first responders (FRs) to selected low-risk 9-1-1 requests for emergency medical services. First responders are rapidly-responding fire crews on apparatus without transport capabilities, with firefighters trained to at least a FR level and in most cases to the basic emergency medical technician (EMT) level. Low-risk 9-1-1 requests include automatic medical alerts (ALERTs), motor vehicle incidents (MVIs) for which the caller was unable to answer any medical dispatch questions designed to prioritize the call, and 9-1-1 call disconnects (D/Cs). A before-and-after study of patient dispositions was conducted using historical controls for comparison. During the historical control phase of six months, one year prior to the study phase, basic life support ambulances (staffed with two basic EMTs) were dispatched to selected low-risk 9-1-1 incidents. During the six-month study phase, a fire FR crew equipped with automated external defibrillators (AEDs) was sent initially without an ambulance to these incidents. For ALERTs (n = 290 in historical group vs. 330 in study group), there was no statistical difference in the transport rate (7% vs 10%), but there was a statistically significant increase in the follow-up use of advanced life support (ALS) (1% vs 4%, p = 0.009). No patient in the ALERTs historical group required airway management, while one patient in the study group received endotracheal intubation. No patient required defibrillation in either group. Analysis of the MVIs showed a significant decrease (p < 0.0001) in the patient transport rate from 39% of controls to 33% of study patients, but no change in the follow-up use of ALS interventions (2% for each group). For both the ALERTs and MVIs, the FR's mean response time was faster than ambulances (p < 0.0001). Among the 9-1-1 D/Cs with FRs only (n = 1,028), 15% were transported and 43 (4%) received subsequent ALS care. Four of these patients (0.4%) received intubation and two (0.2%) required defibrillation. However, no patient was judged to have had adverse outcomes as a result of the dispatch protocol change. Fire apparatus crews trained in the use of AEDs can safely be used to initially respond alone (without ambulances) to selected, low-risk 9-1-1 calls. This tactic improves response intervals while reducing ambulance responses to these incidents.