In a series of 25 patients with pseudosarcoma and associated squamous cell carcinoma of the larynx, there was a predominance of elderly (average age 63 years) men (23 to two, male-to-female ratio). Most of the lesions originated from the vocal cord and most were polypoid or pedunculated. The pseudosarcomatous stroma generally predominated, with a relatively diminutive carcinomatous component. Electron microscopic features and enzyme histochemistry of the most recent case suggest that the pseudosarcomatous stroma is a reactive proliferation of histiocytes and fibroblasts, apparently in response to the squamous carcinoma. Follow-up studies indicated that four patients died with contiguous tumor (squamous carcinoma), another 15 died of unrelated causes, and six were alive and free of tumor.