The hydtoboration of a series of α,β-unsaturated carbonyl compounds, including acrolein, methyl-acrolein, β-methyl-crotonaldehyde, cinnamic aldehyde, methyl vinyl ketone, mesityl oxide, crotonic acid, cinnamic acid etc., has been studied, and the saturated monohydric alcohol can be obtained in every instance, but the yields varied from case to case. Thus, to some extent, the diborate type β-elimination, which occurred in the case of the hydroboration of crotonaldehyde, seems to be a general reaction. The distribution of the various products obtained from these reactions was reasonably clarified by the usual electronic and steric considerations.