Conversion of lunar regolith into a plant growth medium is crucial to the development of a regenerative life support system for a lunar base. Simulants must be used to study weathering processes and to develop procedures for the conversion of lunar regolith into a suitable plant growth medium because of the shortage of actual lunar materials.Dissolution studies have been conducted for Johnson Space Center Lunar Simulant-1 (JSCLS-1) to assess levels of plant nutrients and toxic elements. Weathering in water for 150 4 in the presence of atmospheric oygen and carbon dioxide, yielded alkaline solutions with pH near 8.8. Concentrations of most plant nutrients were at levels normally considered acceptable for plant growth. However, nitrogen was deficient, and phosphorus was present at levels typical of unfertilized soils. DTPA extracts indicated possible manganese and zinc deficiencies. Solution metals were at concentrations far below those generally harmful to plants.Results for Minnesota Lunar Simulant (MLS) were similar to those for JCSLS-1. Deficient elements identified were identical, with the exception of zinc which was deficient only for JSCLS-1. Amounts of iron or manganese extracted with DTPA were comparable for the two simulants, even with much higher glass content in JSCLS-1. This suggests that similar minerals control the extractability of iron and manganese. Comparison of results shows that MLS can be used in addition to JSCLS-I for studying important aspects of weathering chemistry.