Methods	Design: Randomized controlled trial
	Recruitment: Potential participants were identified by the housing program case managers or by medical records.
	Setting: 2 Veterans Affairs medical centers, blinded city, US
	Follow‐up: At baseline, midpoint (about 4–6 mo), and endpoint (about 9–12 mo)
Participants	Population: Formerly homeless Veterans housed using housing vouchers (HUD‐VASH)
	Eligibility criteria: having a history of abusing alcohol and/or drugs, having a serious mental illness, and having a history of homelessness
	Sample size: Total n = 166, Intervention n = 85, control n = 81
	Baseline characteristics: “Participants were older mostly men with nearly equal proportions of white and African American Veterans. Modal education status was high school graduate and most were unemployed and unmarried. 40.1% of Veteran participants had been homeless 2–4 times, for 1–3 years (32.7%). There were no statistically significant differences for any baseline characteristics between treated and control group Veterans” ‐Ellison et al., 2020
Interventions	Peer specialist services: Alongside the HUD‐VASH housing vouchers, the peer specialist‐Veteran meetings were designed to focus on mental health and substance use recovery and community integration skills delivered in both 20 “structured” sessions and 20 “unstructured” meetings designed for community engagement and relationship building. The peer specialists were intended to meet with Veterans at their home or in the community for 1 h each week for 40 sessions to occur over the course of 9–12 months. The peer specialists had to be Veterans with significant recovery from mental health issues, which could include substance abuse. Seven male peer specialists were hired over the course of the study, 6 were white and 1 was African American. It was not possible to provide peer specialists matched to sex and racial profiles of the Veterans.
	Treatment as usual: Included the HUD‐VASH housing vouchers, as well as usual care provided by the HUD‐VASH program.
Outcomes	Housing stability: Housing stability was measured with a count of days spent in HUD‐VASH housing within the past 30 days and with a count of days housed that included HUD‐VASH housing and other types of community housing (such as with a friend or parents).
	Mental health: Symptoms of mental illness were identified using the 24‐item Behavior And Symptom Identification Scale (BASIS‐24).
	Substance use: alcohol and drug use were identified using questions from the Addiction Severity Index (ASI).
Notes