Neutron heating sensitivities to cross-section uncertainties were calculated in a controlled thermonuclear reactor (CTR) blanket. For this purpose, the well-known generalized perturbation methods were used. The CTR blanket chosen was representative of current design specifications. Sensitivity profiles were generated for neutron heating in 6Li, 7Li, iron, and niobium to their respective cross sections. Fairly high changes in the neutron heating can be produced by variations in individual cross sections.