Over the past several decades in Pakistan, an increasing number of women with young children are joining the workforce, which is one of the biggest social changes in the later half of the twentieth century. More children are being raised in households where mothers work for pay as compared with the scenario a generation ago. This change has prompted concerns about whether maternal employment poses any risks to children's cognitive development. The purpose of this descriptive comparative study was to compare the cognitive development of toddlers, aged 24-36 months, of working and non-working mothers in Karachi, Pakistan. The Bayley Mental Scale was used as the primary outcome measure. Data were analysed using non-parametric statistics. There was no association between maternal employment status and toddlers' cognitive development. Differences were found in cognitive development by demographic characteristics, which suggested that selected children were more vulnerable, irrespective of their mothers' employment status. (Contains 3 tables.)