The article reviews the literature on synchronous and metachronous multiple primary malignant laryngeal tumors of the same phenotype, of different phenotypes, and of different histogenesis.The development of a second or even third primary cancer involving the same system is not uncommon. For instance, the association of cancer of the larynx with lung cancer has been increasing and can be explained by the presence of common pathogenetic factors acting in the respiratory system.Multiple primary carcinomas of the larynx are not uncommon, but their exact incidence has not been clearly defined. The occurrence of an additional malignancy in the larynx should not necessarily be interpreted as a treatment failure for the initial laryngeal tumor, since the second tumor may represent a de novo primary malignancy. 'The frequency of primary or multicentric neoplastic areas in the larynx is relevant to research work on carcinogenesis and to clinical matters, such as the early detection of a second primary cancer in the respiratory tract.Patients who have had a primary cancer of the respiratory system are particularly prone to develop subsequent primary tumors elsewhere in this system. There is evidence that multiple synchronous tumors may involve the larynx -an observation that points up the relevance of the concept of "field cancerization" or "condemned mucosa" to this anatomic region.Two distinct synchronous or metachronous malignant tumors of the same histologie type (as, for example, tumors exhibiting squamous differentiation) are not rare in the larynx. Honcamp 2 observed 3 squamous carcinomas in the same larynx. Rabbet 3 reported 3 distinct primary cases of multicentric carcinoma of the larynx. Heiner 4 described a patient with 3 separate squamous carcinomas of the larynx. (The third primary malignant lesion was in situ carcinoma.) Thirty of 535 patients (5.6%) followed up over a 5-to 25-year period after treatment for carcinoma of the vocal fold developed a second primary laryngeal carcinoma. 5Second primary laryngeal cancer in limited (Tl or T2) glottic cancer has been observed in patients treated with different modalities -surgery or radiotherapy -and the incidence of a second primary laryngeal cancer is higher in the group of patients treated with surgery. In particular, in the group treated with surgery (118 patients), 9 of the 32 second primary cancers occurred in the larynx; in the group of irradiated patients (185 patients), 1 of the 23 second primary cancers occurred in the larynx. New malignancies occurring within the larynx were classified as second primary tumors if they occurred more than 5 years after treatment. 6