A bone plate system having a retainer for resisting back-out of a bone anchor from a throughbore of a bone plate is provided. In one aspect, a bone plate system having a resilient retainer disposed in a bone plate throughbore with a pair of elongate arm portions of the resilient retainer extending along opposite sides of the throughbore. In another aspect, a bone plate system having a resilient retainer with a pair of elongate interference portions completely exposed in the throughbore and spaced from each other across the throughbore to retain a head of a bone anchor received in the throughbore. In addition, a bone plate system having a resilient retainer with a pair of opposite end portions disposed within a groove of a throughbore wall such that a bone anchor may be inserted into the throughbore without contacting either of the opposite end portions of the retainer.