  We have measured the superconducting transition temperature $T_c$ of Ni/Nb/Ni
trilayers when the magnetizations of the two outer Ni layers are parallel (P)
and antiparallel (AP). The largest difference in $T_c$ occurs when the Nb
thickness is just above the critical thickness at which superconductivity
disappears completely. We have observed a difference in $T_c$ between the P and
AP states as large as 41 mK - a significant increase over earlier results in
samples with higher $T_c$ and with a CuNi alloy in place of the Ni. Our result
also demonstrates that strong elemental ferromagnets are promising candidates
for future investigations of ferromagnet/superconductor heterostructures.
