Conventional cost accounting assumes that the relation between cost and volume is symmetric for volume increases and decreases. We test an alternative model where costs increase more when activity rises than they decrease when activity falls by an equivalent amount. We find, for a sample of Brazilian firms that selling, general, and administrative costs increase 0.59% per 1% increase in sales but decrease only 0.32% per 1% decrease in sales. We test several hypotheses about the properties of sticky costs and how the stickiness of SG&A costs changes with firm circumstances and we confirm cost stickiness for Brazilian firms.