In a protein interaction screen, we identified the LIM domain protein Smallish (Smash) as a binding partner of Baz. Mutation of smash affects the planar polarized localization of several actomyosin-associated proteins. smash null allele mutants show reduced membrane tension, whereas overexpression of Smash leads to apical constriction in epithelial cells, pointing to a function of Smash in regulation of actomyosin contractility. smash null mutant embryos show strong epithelial morphogenesis defects, consistent with a general reduction in cortical tension