There have been a series of nationally representative surveys in Zambia between 1996 and 2003 that contain information on sexual behaviour in the general population. These show that risky sexual behaviours have become less common. There is evidence of a decline in reported early sexual debut. In a generalized epidemic the sexual behaviour of married people, and the similarity of behaviour patterns within couples, may become an important determinant of HIV transmission. Using Demographic and Health Survey data, the behaviours of married couples were compared between 1996 and 2001/2. Over this period there was less change in the risk behaviour of married couples than in the total survey population. The risk behaviours that showed a significant decline were sex with more than one partner in the last year (men only) and sex before the age of 15. Married couples became more similar to each other with respect to sex before the age of 15. Marital status changed over this period. Monogamously married couples in 2001 were less likely to have the same history of previous marriage than those in 1996. There was an increase in the proportion of men in monogamous second marriages. The distribution of women’s marital status did not change. These changes are consistent with increases in adult mortality (a consequence of increases in HIV prevalence) and suggest that marital dynamics are changing in Zambia. Marriages (either polygamous or monogamous) in which the man has been married before are becoming more common. HIV testing is uncommon: in 2001 only 3% of couples had both been tested for HIV infection. HIV prevalence has remained stable in Zambia between 1996 and 2001. If the declines in risk behaviour that have been observed in this period do not eventually lead to a decline in HIV prevalence this may indicate that the transmission patterns of HIV have changed. The data on marital history are not sufficiently detailed to fully characterize the changes that have taken place in Zambia. However the results suggest that this is an area which needs further investigation; HIV prevention and surveillance efforts may need to pay more attention to married people as behaviour change and increases in HIV associated mortality begin to change the dynamics of marriage.