Experimental work on the three-dimensional Ising ferromagnet Fe[S2CN(C2H5)2]2Cl is reviewed, and magnetic susceptibility and sublattice magnetization2 data are analyzed with correction-to-scaling terms included. Critical exponents γ = 1.165±0.03 and β = 0.245±0.02 are found, assuming modified power law expressions χ0 = Γt−γ (1+aχtΔ) and m(T/TC) = B‖t‖β(1+aM ‖t‖Δ) with correction exponent and amplitudes, Δ = 0.493, aχ = 0.207, and aM = 0.156. The critical amplitudes are found to be Γ = 1.47±0.07 emu/mole (Γr = 1.07±0.05 for the reduced susceptibility) and B = 1.30±0.05. Γ is larger than most theoretical estimates for the Ising model on three-dimensional lattices, while B is smaller than theoretical results. The amplitude ratio Γr/B is 0.83±0.07. Theoretical values for this ratio are not universal but exhibit only a weak lattice dependence, and are in the range from 0.65 to 0.71 for the three-dimensional Ising model. Heat capacity data are sparse and less reliably analyzed, but appear to suggest abnormally large values of α (≳0.3) and rather small values of A (0.2–0.5) in C/R = At−α+ B′. Including a correction-to-scaling term does not alter this conclusion. The ratio RC = AB−2Γr is in the range from 0.12 to 0.33, substantially less than the theoretical value 0.474 for this universal quantity in the three-dimensional Ising model. Neither the possible presence of multispin interactions nor a nondiverging AF contribution to the susceptibility appear to be adequate to account for the unusual critical behavior observed in this system. a)Acknowledgment is made to the donors of The Petroleum Research Fund, administered by the ACS, for partial support of this research. 1 G. C. DeFotis, F. Palacio, and R. L. Carlin, Phys. Status Solidi B 95, 380 (l978). 2 G. C. DeFotis and J. A. Cowen, J. Chem. Phys. 73, 2120 (1980).