This is a phase IIb, randomised (study medication is assigned by chance), double-blind (neither the patient nor the study physician will know to which treatment group the patient is assigned) trial to assess the neuropsychiatric adverse event profile of etravirine (ETR) 400mg once daily versus efavirenz (EFV) 600mg once daily, each in combination with an investigator-selected background of 2 other anti-HIV drugs of the class nucleoside/nucleotide reverse transcriptase inhibitors (N[t]RTIs). The combination of N[t]RTIs to be chosen by the study physician can be abacavir (ABC)/lamivudine (3TC), zidovudine (AZT)/lamivudine (3TC) or tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC). Approximately 150 Human Immuno-deficiency Virus type 1 (HIV-1) infected patients, who have never received any antiretroviral (ARV) treatment will be randomly assigned (like tossing a coin) to either the etravirine treatment group or the control group (efavirenz). The study period includes a screening period of maximum 6 weeks, a 48 week treatment period, an additional 2-8 weeks treatment until unblinding (study physician (and patient) will receive information to which treatment group the patient is assigned), followed by a 4 weeks follow-up period. The main purpose of this study is to gather further data on how many, how often, and how severe the central nervous system and psychiatric (neuropsychiatric) events are between the two treatment groups. In addition, the study will look at overall safety, tolerability and antiviral effectiveness between the two treatment groups. During the trial, patients' health will be monitored by physical examination, checking of vital signs (blood pressure / pulse), and laboratory testing on blood and urine samples. Also blood samples will be drawn to measure the antiviral effectiveness (i.e., decrease of the plasma viral load to a level <50 HIV-1 RNA (ribonucleic acid) copies/mL), immunology assessments (to assess the body's immune system) and pharmacokinetic (to measure the drug level in blood) analysis of etravirine. Patients will be asked to complete the "HIV Patient Symptoms Profile" (HIV PSP) Questionnaire at each visit, which contains questions relating to the impact on patients' current health and well-being. The study hypothesis is that the proportion of patients with at least one neuropsychiatric adverse event related to the study drug, observed between start of treatment (Baseline; BSL) through Week 12, is significantly lower in the etravirine group than in the efavirenz group. Patients will be taking blinded medication twice a day, administered orally (by mouth). Only one of the blinded doses will contain an active ingredient. Etravirine 400mg (or dummy-pills) - 4 tablets - should be taken once a day, following a meal, preferably breakfast. Efavirenz 600mg (or dummy-pill) - 1 tablet - should be administered once daily on an empty stomach, preferably at bedtime.The intake of the investigator-selected N[t]RTIs should be taken as instructed by the investigator.