We present a comprehensive set of state-to-state rate constants for the relaxation of isolated rotational levels of NH and ND in their (c (1) Pi,upsilon = 0, J) states in the presence of colliding He and Ar. The rotational states were populated in pulsed photolysis experiments by excitation on single (c,upsilon’=0, J’<--a,upsilon "=1, J ") transitions. Fluorescence spectra of the (c,upsilon>’=0-->a,upsilon "=0) transitions were recorded to determine the relative populations caused by inelastic collisions. The master equation of the relaxation processes was solved iteratively to yield single collision rate constants. Additionally, time profiles were recorded. Rate data on the 8 and 12 lowest rotational levels are furnished for NH(c) and ND(c), respectively. These data are compared with previous results on BH(A (1) Pi) and NH and PH in their (A (3) Pi) states. The rate constants for rotational energy transfer can be represented by the exponential gap law.