To determine the prevalence of HIV associated Neurological Disorder (HAND) in a population of HIV positive patients within a primary care setting compared with the HIV negative population. The investigators aim is to assess the use of optimal screening methods to assess HAND. For this the investigators will be comparing the performance of a group of persons who are HIV positive and a group of persons who are HIV negative to test their memory and concentration abilities over-time.

HIV positive Inclusion Criteria:

• Documented HIV infection
• Able to participate in study procedures

HIV positive Exclusion Criteria:

• Inability to comprehend or read English (as established by the English proficiency questionnaire)
• Drug or alcohol intoxicated (as determined by the investigator)
• Lack of information in medical records to determine the HAND predictive algorithm (current CD4 count, past CNS HIV-related disease, and duration of HIV therapy)
• Life expectancy <6 months
• Inability to attend the clinic for required study follow up visits

HIV-negative Inclusion Criteria:

• Negative HIV-1 test within 12 months of study entry

HIV-negative Exclusion Criteria:

• Life time traumatic brain injury leading to loss of consciousness of at least 30 minutes.
• Inability to comprehend or read English (as established by the English proficiency questionnaire).
• Inability to attend the clinic for required study follow up visits.
• History of chronic neurological illness.
• Unstable psychiatric conditions such as bipolar disorder or depression.
• Individuals with psychiatric disorder on the psychotic axis.
• Active or past (within the last 6 months) severe alcohol or substance abuse sufficient, in the investigator's judgement, to prevent completion of tests or Inability to attend for the planned required study follow up visits.

Patients attending Holdsworth House Medical Practice, Sydney, Australia