BACKGROUND:To the authors' knowledge, little work has been done to estimate the time costs associated with informal caregiving for cancer survivors.METHODS:Data from a national survey of caregivers of cancer patients in 2003 to 2006 were used to estimate the time associated with informal caregiving in the 2 years after patient diagnosis with bladder, breast, colorectal, kidney, lung, melanoma of the skin, ovarian, prostate, or uterine cancer, or non‐Hodgkins lymphoma (NHL). Caregivers reported the duration and daily intensity of caregiving as well as the types and frequency of support provided. The median wage rate in 2006 ($16.28) was used to value caregiver time, and other methods to value time were evaluated with sensitivity analyses.RESULTS:On average, caregivers provided care for 8.3 hours per day for 13.7 months. The number of months and daily hours spent caregiving were the highest for cancer survivors diagnosed with distant disease compared with survivors with regional or localized disease (P < .05). Approximately half of caregivers provided emotional, instrumental, tangible, or medical support, although the frequency varied dramatically. Informal caregiver time costs over the 2‐year period after diagnosis were the highest for caregivers of patients diagnosed with lung ($72,702; 95% confidence interval [95% CI], $56,814‐$88,590) and ovarian ($66,210; 95% CI, $40,750‐$91,670) cancers and NHL ($59,613; 95% CI, $43,423‐$75,803) and the lowest for caregivers of patients with breast cancer ($38,334; 95% CI, $31,442‐$45,226).CONCLUSIONS:Time spent by informal caregivers was substantial and was an important component of the burden of cancer care. Incorporation of the value of informal caregiver time will be important when evaluating the costs and benefits of cancer control interventions. Cancer 2009;115(18 suppl):4362–73. © 2009 American Cancer Society.