A state-resolved experimental investigation of the rotational relaxation of the NH(A (3)Pi,v=0) radical in inelastic collisions with ammonia is presented. Fine structure and Lambda-doublet resolved, state-to-state rate constants were extracted from NH(A (3)Pi,v=0-->X (3)Sigma(-),v=0) fluorescence spectra recorded upon laser excitation to individual levels (N,F-j,e/f ) (j=1-3) in the A (3)Pi,v=0 state. Relaxation trends are reported with regard to Hund's coupling (a), (b), and intermediate cases. At low N, the most dominant process is the Lambda-doublet mixing. For high N, rotational relaxation proceeds predominantly via DeltaN=-1 transitions at conservation of the spin unit and the A(')/A(') symmetry. A general tendency of conservation of the spin unit (DeltaOmega=0) is observed. A comparison of the dipolar collision partner NH3 with the spherical He is performed.