A transition in the mechanism and kinetics of slow crack growth (SCG) is described in this paper. It resembles wellknown ductile-brittle transition in dynamic impact resistance and referred to as ductile-brittle transition of second kind (DBT2). There is a corresponding transition temperature (TT2). A discontinuous, stepwise crack propagation and continuous slow crack growth (SCG) are recorded above and below TT2, respectively. Optical and SEM observations suggest that the change of SCG mechanism is closely associated with material ability to form a stable process zone (PZ) in front of growing crack. The Paris-Erdogan equation expressing the average crack growth rate as a power function of stress intensity factor has noticeably different power at the temperatures above and below TT2. In addition, the crack growth rate normalized by a characteristic strain rate is orders of magnitude higher at temperatures below TT2 than that above TT2. Such transition in kinetics of SCG has an apparent consequence in duration of SCG stage prior to ultimate failure. The observed TT2 appears to be significantly higher than conventional ductile-brittle transition temperature in dynamic impact. TT2 also implies certain limitations for extrapolation of elevated temperature SCG data to ambient temperature commonly used in temperature accelerated testing.