After having verified that buclizine was capable to promote the growth of malignant tumours by up to 33 per cent, rats and mice were treated with this substance in doses which lie below the acute sublethal, but very much above the therapeutical dose. Occasionally, some tumours appeared, namely a fibrosarcoma in Wistar rats and undifferentiated sarcoma and a papillary adenoma in Swiss mice. The first tumour appeard in 1970 and was designated as "BUSP" (BUclizine-SPoladore). It could beeasily maintained until this date. Its characteriscis are: slow growing, permitting the bearer´s survival for about three months; the weight reaches about 125g in the final stage; intense peritumoral hyperemia; a massive tumour almost without necrosis in the central part; occuring freely between the skin and the subjacent tissues during its whole evolution.