Intellectual ability is assessed with the Spot-the-Word (STW) test (A. Baddeley, H. Emslie, & I. Nimmo Smith, 1993) by asking respondents to identify a word in a word-nonword item pair. Results in moderate-sized samples suggest this ability is resistant to decline due to dementia. The authors used a 3-parameter item response theory model to investigate the measurement properties of the STW in a large community-dwelling sample (n = 2,480) 60 to 64 years of age. A number of poorly performing items were identified. Substantial guessing was present; however, the number of words correctly identified was found to be an accurate index of ability. Performance was moderately related to a number of tests of cognitive performance and was effectively unrelated to visual acuity and to physical or mental health status. The STW is a promising test of ability that, in the future, may be refined by the deletion or replacement of poorly functioning items.