The short term memory binding task (STMB) was shown to be impaired at baseline testing in asymptomatic/preclinical mutation carrier members of autosomal dominant Alzheimer's disease (AD) kindreds (Parra et al, Brain 2010). The apolipoprotein E (APOE) e4 allele is the most prevalent genetic risk factor for AD. We therefore asked whether the STMB might be similarly sensitive to preclinical AD in APOE e4 carriers. The STMB is a visual memory paradigm in which patients must detect changes in a target array involving one or multiple (binding) properties. Together with standard neuropsychological tests, the STMB was administered to 50-79 year old members of the Arizona APOE Cohort to encompass the age range of those that previous biomarkers studies have shown to be at risk for harboring preclinical AD but who were cognitively normal at the time of their most recent followup visit. 97 APOE e4 carriers and 112 noncarriers did not differ in age (65.8+/-6.9 years), education (16.0+/-2.4 years), or gender (69.9% women). Carriers overall performed less well on a measure of shape accuracy (82.4 v 87.7%, p=.0008), as well as on standard memory measures (including the auditory verbal learning test, selective reminding test, logical memory, and complex figure test) and a block design task, among other tests. The differences between noncarriers and heterozygotes (p=.004) and homozygotes (p=.004) were each significant with a significant e4 gene dose effect (p=.003). Additionally shape-color binding accuracy was disrupted in homozygotes (65.0 v 69.7%, p=.038). Within the course of the STMB test epoch, 12 participants met Petersen criteria for mild cognitive impairment (MCI) and showed reduced shape accuracy (74.4 v 85.2%, p=.002) and shape-color binding accuracy (59.9 v 68.4%, p=.007). After excluding these 12 subjects, no comparisons (STMB and otherwise) remained significant, although there remained a trend for reduced shape accuracy among e4 carriers (p=.07). Shape and shape-color binding accuracy in visual memory are sensitive indicators of early stage MCI, as are other neuropsychological measures, but all were less sensitive to presymptomatic stage AD in APOE e4 carriers.