Samples of R7T7 nuclear waste glass were leached for 35, 120 and 427 days at 190°C in NaCl dominated brine. The alteration layer at the glass surface consisted of a mixture of amorphous and crystalline phases. The amorphous phase retained Zr, U and Nd. The crystalline reaction products were: powerllite, coffinite, analcime, quartz, barite, anhydrite and saponite. The chemical composition of the alteration layer did not appear to vary significantly between 35 and 427 days. The calculated chemical budgets show that the loss of elements to the solution decrease with increasing reaction progress due to the precipitation of the secondary phases. The results of the electron microscopy analysis of these laboratory experiments agree well with the in situ alteration results of R7T7 glass in an underground saline environment in the Salado Formation of New Mexico.