This paper identifies variations in the age and gender characteristics of informal carers in the UK. The paper is based on the Individual Sample of Anonymous Records, a 3% random sample of the 2001 UK Census. The sample size was 1 825 595. Of this sample, 10% were reported to be carers. The analysis shows that informal caregiving is systematically linked with both age and gender. Caregiving increased with age until reaching a peak in the 45–59 age group, in which almost 20% were carers. Similarly, the amount of time spent caregiving increased with age, with the highest levels of caregiving commitment in people aged 80–89 years. Regarding gender, 11.3% of women were carers compared to 8.6% of men and overall women committed more time to caregiving than men. However, this pattern was reversed in later life (70+), where there was a higher proportion of carers and greater time commitment to caregiving amongst men. While the predominance of women as informal carers has been well reported, the importance of men as informal carers in old age is much less commented upon. This study thus suggests that informal caregiving is most prevalent in groups of the population that, according to previous research, may experience most strain from doing so: elderly people who may be frail and often are in a spousal relationship with the care-recipient, and middle-aged women with multiple roles. Therefore, it is of great importance that their particular needs and circumstances are fully taken into account both in the development of formal support and when information about available support is targeted.