Attention deficits are a prominent aspect of cognitive dysfunction after mild traumatic brain injury MTBI. Patients frequently complain of distractibility and difficulty attending to more than one thing at a time, and several neuropsychological studies have found evidence for a specific attention deficit without general neuropsychological impairment. The present study examined the nature of attentional disturbance after MTBI using an extended version of the 2 and 7 Test, which introduced two conditions reflecting patients' subjective complaints: the ability to perform with background 'noise', and while simultaneously attending to a secondary task. The dual task demands produced a significant slowing in processing speed for both the MTBI patients and control subjects. However, the relative decline in processing speed appeared much greater for the patients with MTBI, and they differed from control subjects only in this condition. The results are consistent with findings that patients with MTBI exhibit relatively subtle cognitive deficits which are apparent primarily under conditions which require effortful or controlled cognitive processing and exceed their available cognitive resources. Thus, the attentional deficits apparent during dual task demands may represent decreased cognitive, and perhaps neural, efficiency which reflects MTBI patients' subjective complaints and functional impairments.