The Kidnappers Slide complex, on the 1–5° upper continental slope of eastern North Island, New Zealand, consists of several, very large translational slides and rotational slumps. They are of several Late Quaternary phases, range from 20 to 140 m thick, and cover a total area of 720 km2. The main, early Holocene (c. 8000–10,000 yr) phase involved a coast‐parallel sedimentary prism that was deposited on the outer shelf and upper continental slope at a rate of 1–3 m/1000 yr during the last glacial age. Irregularly blanketing the slump, and also locally slumped, is the thin, outer edge of the post‐glacial (< 16,000 yr) prism, deposited on the upper slope at rates ranging from 0.3 to 0.7 m/1000 yr. The sediments consist essentially of terrigenous hemipelagic olive gray mud, along with minor sandy mud, volcanic ash, and pumiceous mud. They are low in calcium carbonate and are inorganic, with high plasticity and low sensitivity. Minor variations occur in the mass physical properties of the post‐glacial sediments, both regionally and with burial depth, and between the post‐glacial and last‐glacial sediments. The sediment profile is inferred to be normally consolidated, except for the top 1 m, which exhibits overconsolidation. Laboratory consolidated‐drained direct shear tests and consolidated‐undrained triaxial tests show that the slopes in the region are stable under static conditions and that there is little regional variation in static strength. Consolidated‐undrained cyclic triaxial tests, however, show that during severe cyclic loading the shear strength of sediments sampled from disturbed slopes is reduced by up to 15% relative to the static strength values. In contrast, sediments from steeper, undisturbed slopes south of the complex are not susceptible to strength degradation during cyclic loading. A simple infinite slope stability analysis indicates that slopes in the region may become unstable during large magnitude earthquakes capable of generating ground accelerations exceeding 14% of gravity.