The 6 day subrenal capsule (SRC) assay was performed in normal mice using 20 fresh human non-small cell lung cancers and nine fresh ovarian cancers. Different multi-agent chemotherapy regimens administered intravenously on days 2 + 3 of the assay were evaluated for activity against these two tumor types. Macroscopic results measured via an ocular microscope showed high activity for some combinations as well as for single agents. However, when subjected to microscopic examination, the SRC implants in the untreated control animals did not show viable tumor growth on day 6. Detailed histologic evaluation of over 800 SRC grafts reveals an intense inflammatory and fibrotic reaction in the majority of the grafts. These results indicate that drug sensitivity patterns obtained with this assay using only macroscopic criteria do not correlate with actual tumor regression. Microscopic analysis of the grafts prior to transplant shows absence or only minimal presence of tumor in many cases which also contributes to the poor growth observed in these two tumors.