BACKGROUND: Lifelong antiretroviral therapy (ART) for pregnant and breastfeeding women (Option B+) was rolled out in Zimbabwe from 2014, with simultaneous raising of the CD4 treatment threshold to 500 cells per cubic millimeter in nonpregnant/breastfeeding adults and children 5 years and over. METHODS: Lablite is an implementation project in Zimbabwe, Malawi, and Uganda evaluating ART rollout. Routine patient-level data were collected for 6 months before and 12 months after Option B+ rollout at a district hospital and 3 primary care facilities in Zimbabwe (2 with outreach ART and 1 with no ART provision before Option B+). RESULTS: Between September 2013 and February 2015, there were 1686 ART initiations in the 4 facilities: 91% adults and 9% children younger than 15 years. In the 3 facilities with established ART, initiations rose from 300 during 6 months before Option B+ to 869 (2.9-fold) and 463 (1.5-fold), respectively, 0-6 months and 6-12 months after Option B+. Post-Option B+, an estimated 43% of pregnant/breastfeeding women needed ART for their own health, based on World Health Organization stage 3/4 or CD4 ≤350 per cubic millimeter (64% for CD4 ≤500). Seventy-four men (22%) and 123 nonpregnant/breastfeeding women (34%) initiated ART with CD4 >350 after the CD4 threshold increase. Estimated 12-month retention on ART was 79% (69%-87%) in Option B+ women (significantly lower in younger women, P = 0.01) versus 93% (91%-95%) in other adults (difference P < 0.001). CONCLUSIONS: There were increased ART initiations in all patient groups after implementation of World Health Organization 2013 guidelines. Retention of Option B+ women was poorer than retention of other adults; younger women require attention because they are more likely to disengage from care.