To study the influence of 'visitor presence' on captive lion-tailed macaques, a behavioural study (Short Term Effects) was conducted on 30 individuals housed in 8 zoos across India. The study animals were observed on 'visitor presence' days and on 'visitor absence' days, which were zoo holidays. To record the long-term impact of 'visitor presence' on captive primate behaviour, a study on the Long Term Effects was also conducted. In this study, the behaviour of seven singly-housed individuals was recorded independently when 'on-exhibit' and 'off-exhibit' in enclosures of similar sizes. In the Short Term Effects, visitors influenced 20% more abnormal behaviour and 3% more social, mating and aggressive behaviours. In the study on Long Term Effects, visitors were found to influence a 30% increase in abnormal behaviour, In addition, in this study on Long Term Effects, use of space in the enclosure varied with individuals using the areas of the enclosure with trees, shrubs and water bodies (enriched zone) more when 'off-exhibit' than when 'on-exhibit'. 'Visitor presence' was thus found to influence the behaviour of captive lion-tailed macaques in a negative way suggesting that 'visitor presence' might adversely affect their welfare. (c) 2005 Elsevier B.V. All rights reserved.