The aim of this paper is to test for stochastic monotonicity in intergenerational socio-economic mobility tables. In other words, we question whether having a parent from a high socio-economic status is never worse than having one with a lower status. Using existing inferential procedures for testing unconditional stochastic monotonicity, we first test a set of 149 intergenerational mobility tables in 35 different countries and find that monotonicity cannot be rejected in hardly any table. In addition, we propose new testing procedures for testing conditional stochastic monotonicity and investigate whether monotonicity still holds after conditioning on a number of covariates such as education, cognitive and non-cognitive skills. Based on the NCDS cohort data from the UK, our results provide evidence that monotonicity holds, even conditionally. Moreover, we do not find large differences in our results when comparing social class and wage class mobility. Copyright © 2010 John Wiley & Sons, Ltd.