The complications following the use of laryngeal mask(LM) are usually mild and cause clinical problems rarely. However, as the use of LM increases, it seems important to know the common injuries, symptoms, and factors relevant to complications from its use. We investigated prospectively the influence of age, sex, height, weight, duration of LM placement, presence of blood tinged on LM and coughing on LM placement, use of anticholinergics, anticholinesterase, and opioid on the mucosal injuries and patient symptoms in 97 healthy adult patients undergoing elective surgery by the indirect laryngoscopy and questionnaire 8~24 hours after surgery. The upper airway symptoms were throat discomfort(22.7%), and sore throat(10.3%). The findings of mucosal injuries were erythema(27%), edema(5%), and petechial hematoma(2%). The mucosal injuries were centered around the pharynx and the epiglottis(63.6% of total mucosal injuries), and 17 of 21 patients who were observed to have mucosal injuries complained upper airway symptoms. These resuts suggest that the pharynx and epiglottis are most vulnerable to injuries and most common sites causing upper airway symptoms from the LM placement. Vocal cord erythema was found in 8.2% of patients, which was seemed to be due to the grates of the LM aperture. The severity of the mucosal injuries was correlated to the severity of upper airway symptoms(P < 0.05, r=0.464). Male sex, presence of blood on LM, and the longer duration of LM placement were associated with a relatively high incidence of mucosal injuries, and the longer duration of LM placement with that of upper airway symptoms(P < 0.05). After above variables were controlled for, presence of blood on LM was a precipitating factor in mucosal injuries and the longer duration of LM placement was precipitating factor in symptoms(P < 0.05). We failed to find a significant correlation of duration of LM placement with the severity of mucosal injuries or symptoms.