Despite work to prevent and reduce homelessness over the last 15 years, the number of homeless persons in Norway has remained stable since the first mapping of homelessness was published in 1997. We conducted a systematic review on the effectiveness of housing programs and case management to improve housing stability and reduce homelessness among people who are homeless or at risk of becoming homeless. The results of the review are based on evidence from 43 randomized controlled studies. The key findings show that high intensity case management is probably better than usual services at reducing the number of people who are homeless. The program called Housing First is probably better than usual services at reducing homelessness, improving housing stability and increasing the amount of time in housing. Furthermore, the following interventions may be better than usual services at reducing homelessness and/or improving housing stability: Critical time intervention. Abstinence-contingent housing. Non-abstinence-contingent housing with high intensity case management. Housing vouchers. Residential treatment. It seems that many of these interventions may have similar beneficial effects, and it is unclear which of these is best with respect to reducing homelessness and increasing housing stability. We found that a range of different housing programs and case management interventions appear to improve housing stability and reduce homelessness compared to usual services. The findings showed no indication of housing programs or case management resulting in poorer outcomes for homeless or at-risk individuals than usual services.