Wherever you are, hotel taxis are generally the best and safest option, although they can be expensive. Carry small bills; drivers rarely have change; some destinations have rather high minimum fares. Always let your hotel or restaurant call a taxi for you. Don't use "street" or gypsy taxis, which are often in poor repair and can be a security risk. Recommendable radio-taxi companies in Santo Domingo are Tecni-Taxi (which also operates in Puerto Plata) and Apolo. Most taxis will also carry you out of town and will have rate charts for major destinations; just be aware that these private taxi transfers can be expensive (well over US$100) for a destination that's less than hour away and more for destinations further afield.
DominicanShuttles provides safe and reliable long-distance private taxi service, but trips must be arranged in advance online (as little as 24 hours or as much as weeks in advance in the case of a long-distance airport transfer).
Apolo Taxi. Santo Domingo, Nacional. 809/537–0000; 809/537–1245; www.apolotaxi.com.
Taxi-Cabarete. Cabarete, Puerto Plata. 809/571–0767.
Taxi-Queen Santiago. Santiago, Santiago. 809/570–0000.
Taxi-Sosúa. Sosúa, Puerto Plata. 809/571–3097.
Tecni-Taxi. 809/567–2010; 809/320–7621.