Legislation laying down a legal limit for blood alcohol concentration was introduced in New South Wales in 1968, but has had a disappointing effect on drink-driving behaviour. This survey was designed to examine what factors might be preventing the law's operating as an effective deterrent, and to obtain essential information for the planning of countermeasures to alcohol-related crashea Interviews were conducted with 1197 men and women, aged between 17 and 69 years, distributed at random through the Sydney metropolitan area. Results included the following findings: seven out of ten men at least sometimes combine drinking and driving, many of them frequently, but only two out of ten women; the group containing the highest proportion of drinking drivers is young men; six out of ten young men admitted to driving after drinking too much; the commonest place to drink away from home is the pub, but men usually drive themselves home afterwards and very rarely use alternative means of transport; young men are more likely to feel pressures to keep up with mates when drinking at a pub; half the respondents did not include alcohol in a list of the three most important factors which in their view contributed to serious traffic accidents; many men overestimate the amount of beer they can drink and still be safe to drive; there is widespread ignorance as to the legal limit for blood alcohol; the legal limit is not seen to be related to safe driving; eight of ten male drivers who drink said the new legislation had not changed their drinking-driving habits. Driving after drinking appears to be customary behaviour for men, and thus attempts to reduce alcohol-related accidents by reducing the combined incidence of drinking and driving in the community will come into direct conflict with social custom. Social pressures now exist which ensure that the custom of driving after drinking too much is likely to persist in certain sections of the male population. The present results suggest that ignorance and misinterpretation of the drink-driving law may be contributing to widespread opposition to it. Many men, especially young men, are resentful of what they see as an unrealistic attempt to set an arbitrary limit on their drinking.