An experimental method is demonstrated for the determination of internal quantum efficiency (IQE) in III-nitride-based light-emitting diodes (LEDs). LED devices surrounded with an optically absorbing material have been fabricated to limit collected light to photons emitted directly from the quantum wells across a known fraction of the recombination area. The emission pattern for this device configuration was modeled to estimate the extraction efficiency. IQE can then be calculated from the measured input current and output power. This method was applied to c-plane In(x)Ga(1-x)N-based LEDs emitting at 445 nm. Initial measurements estimate an IQE of 43%+/- 1% at a current density of 7.9 A/cm(2).