Abstract. An explicit description of the basic Lagrange polynomials in two variables related to a six-tuple $a^1,\dots ,a^6$ of nodes is presented. Stability of the related Lagrange interpolation is proved under the following assumption: $a^1,\dots ,a^6$ are the vertices of triangles $T_1,\dots ,T_4$ without obtuse inner angles such that $T_1$ has one side common with $T_j$ for $j=2,3,4$.
Keywords. Quadratic Lagrange interpolation in 2D, stability