Data on the activity, selectivity, and reaction conditions for the selective oligomerization of ethylene to octene-1 mediated by chromium-containing organic compounds in combination with organoaluminum compounds have been summarized and analyzed. Possible schemes for the mechanism of the formation of octene-1 and byproduct cyclic hydrocarbons (methylenecyclopentane and methylcyclopentane) and higher (> C-8) linear olefins have been briefly discussed.