Abstract. Here we consider results concerning ill-posedness for the Cauchy problem associated with the Benjamin-Ono-Zakharov-Kuznetsov equation, namely,
y).For k = 1, (IVP) is shown to be ill-posed in the class of anisotropic Sobolev spaces H s 1 ,s 2 (R 2 ), s 1 , s 2 ∈ R, while for k ≥ 2 ill-posedness is shown to hold in H s 1 ,s 2 (R 2 ), 2s 1 + s 2 < 3/2 − 2/k. Furthermore, for k = 2, 3, and some particular values of s 1 , s 2 , a stronger result is also established.