A pyroantimonate precipitation reaction was utilized for localization of calcium, magnesium, manganese, potassium, and zinc ions inCucurbita pepoL. infected bySclerotinia sclerotiorum(Lib.) de Bary. Precipitation sites were easily observed in the cytoplasm adjacent to the cell walls, in the vacuoles, and to a lesser extent, in chloroplasts. The precipitate was analyzed for antimony content using energy dispersive X‐ray microanalysis. Counts of 5 channels of the La antimony peaks were analyzed. Electron dense precipitation sites in vacuoles had counts which averaged an order of magnitude greater than counts of cell walls and chloroplasts. Calcium deficient plants had the least amount of precipitation in cell walls and chloroplasts. Observed electron density in sections was not necessarily correlated with counts.