  We present high resolution spectroscopic data of the two giant extragalactic
H II regions NGC 5461 and NGC 5471 in M101, which have been obtained with the
2.1-m telescope of the Observatorio Astron\'omico Nacional in San Pedro
M\'artir, Baja California. We measured the intensities of several H and He
recombination lines, and of forbidden lines of a large number of ions. We
calculate the physical conditions in the two nebulae with a large number of
diagnostics and determine their chemical abundances by applying ionization
correction factors icf's to the observed ionic abundances. For NGC 5461, the
icf's are based on a tailored photoionization model of the region (Luridiana &
Peimbert 2001), while for NGC 5471 they are computed from those predicted by a
photoionization model of NGC 2363 (Luridiana, Peimbert, & Leitherer 1999), a
region which is similar to NGC 5471 in the ionization structure. For both
regions, the icf's are compared to those computed following the prescriptions
by Mathis & Rosa (1991). Such comparison shows large discrepancies for several
elements, including nitrogen, neon, and chlorine.
