Children in low- and middle-income countries (LMIC) are the least touched by recent successes in the diagnosis and treatment of HIV/AIDS globally. Early treatment is essential for a child's longer and higher quality of life; however, by 2011, only a small proportion of HIV-seropositive children in LMIC countries were receiving treatment, in part because of persisting low rates of diagnosis. This study of the prevalence and characteristics of children tested for HIV was embedded in the Coping with HIV/AIDS in Tanzania (CHAT) study in which HIV-seropositive and HIV-seronegative adults, and adults with unknown HIV status were asked about HIV testing for their children. Data were gathered from November 2009 to August 2010 during the scale-up of Prevention of Mother To Child Transmission and Early Infant Diagnosis programs in the region. Reports on 1776 children indicate that 31.7% of all children were reported to have been tested, including only 42.9% of children with an HIV-seropositive caregiver. In general, children more likely to be HIV tested were biological children of study participants, younger, of widowed adults, living in urban areas, and of HIV-seropositive parents/caregivers. Children belonging to the two indigenous tribes, Chagga and Pare, were more likely to be tested than those from other tribes. Rates of testing among children less than two years old were low, even for the HIV-seropositive caregiver group. The persistence of low testing rates is discussed in terms of the accessibility and acceptability of child testing in resource poor settings.