Neuroblastoma, a neuroendocrine tumor, is the most common cancer in infancy. 75 % of those affected are under the age of 5. The disease is heterogeneous and survival rate is low.   Current treatment of neuroblastoma consists of surgery, radiation and chemotherapy, where the targets for the treatment are the malign cells. Due to the cancer cells instable genome there is a risk for resistance development. This negatively impacts the treatments goal of hindering tumor growth and spread.  Tumor growth is not only determined by malign cells but also the interactions of those tumor cells with tumor vessels and different types of cells in the tumor stroma.   The aim of this paper is to develop a relevant histological method to study the properties of tumor stroma in tumor sections retrieved from human NB tumor xenografts in mice treated with angiogenesis inhibitors SU11657 and Zoledronic acid. The study is a continuation of previous studies with the inhibitors which have shown good effect on tumor growth and angiogenesis on neuroblastoma.   In the short term treatment with SU11657 and Zoledron acid showed that tumor growth declined. In the longer treatment with SU11657 the growth didn’t decline with the same rate compared to the short term treatment. Angiogenesis on the other hand decreased in all the treatments independent of treatment duration. The histological staining with Sirius red revealed that treated tumors had an increased amount of stroma compared to the untreated tumors.   In conclusion the relative increase of tumor volume, decreased number of vessels and expansion of tumor stroma in the longer treatment with SU11657 indicated that tumors might survive the angiogenesis inhibitor treatment through expansion/activation of its stroma. The histological staining with Sirius red in saturated picric acid marked the collagen, i.e. stroma, well and enabled quantification of the stroma.