HIV/AIDS is the fourth most common cause of death in the world  and is estimated to have killed 3.1 million individuals and infected 4.9 million persons in 2005 alone. The number of people infected by HIV is steadily rising and sub-Saharan Africa is the most affected region in the world . Ethiopia has the fifth largest population of HIV-infected individuals living in Africa, which accounts approximately 4% of the world's HIV/AIDS cases .
Highly Active Antiretroviral Treatment (HAART) has dramatically reduced mortality and morbidity due to HIV [4, 5]. It is effective because it reduces HIV replication and hence allows the regeneration of CD4+ T-lymphocyte mediated immune responses [6, 7]. It cannot, however, totally eradicate HIV [8, 9] and hence prolonged viral suppression is essential for long-term efficacy of HAART [10, 11].
Prolonged viral suppression is only achievable if the virus does not get the chance to replicate and develop drug-resistant HIV variants . The virus has the chance to replicate not only if the patient is untreated  but also if the viral replication is not completely inhibited by the treatment (i.e. due to sub-optimal drug exposure) . When replication occurs during treatment, this leads to the development of genetic variation, which in turn leads to the emergence of variants that might be resistant to antiretroviral treatment .
Despite the high prevalence of HIV/AIDS in Africa including Ethiopia, the HAART coverage is extremely low due to limited resources, but in these days WHO as well as different countries are interested to intensify the HAART activities and expand the program as preventive strategy for HIV epidemic and AIDS patient care.
Ethiopia has been started provision of HAART for the people living with HIV/AIDS since August 2003. However, by the end of June 2008, there were only 110,611 patients (75%) who were alive and on HAART out of the 150,136 patients who had been started on HAART since 2003 . This indicates the need for an intervention to reduce the drop-out rate due to either death or loss to follow-up.
One of the main factors contributing to sub-optimal drug levels and resistance is non-adherence to treatment [17, 18]. It has been reported that the patient needs to take a minimum of 95% of prescribed antiretroviral doses in order to avoid resistance development. Patients taking 95% or more of their doses only had a documented virologic failure (i.e. over 400 virus copies/mL in blood) in 22% of the cases compared to 80% of the patients taking less than 80% of their doses .
Patient's readiness to antiretroviral therapy means put the patient himself/herself feels ready to initiate, take responsibility for, and to maintain (including being adherent to) a prescribed treatment . Readiness for treatment can be assessed prior to treatment initiation and hence timely measures can be taken before initiation of therapy, sometimes postponement of treatment may be preferable in order to motivate and increase the degree of readiness, and hence, hopefully, increase the success rate of the treatment .
Assessment of patient adherence and readiness to treatment are good opportunities to enhance patient understanding of medication regimen, to identify potential obstacles to taking medication and trusting relationship between patients and health care providers, and ultimately to prevent virologic break through . Therefore, this study aimed to assess the level and determinants of nonadherence and nonreadiness to HAART among PLWHA at Gondar University Teaching Hospital and Felege Hiwot Hospital in Northwest Ethiopia.