Based on previously published studies, this review describes the pulmonary consequences of marijuana smoking. Smoking of marijuana is significantly associated with chronic bronchitis (cough and phlegm), but it has not been firmly established whether it also leads to a reduction in lung function. Both epidemiological studies and case reports suggest that regular smokers of marijuana have a higher risk of developing malignancies in both the upper and lower airways. Smoking of marijuana contaminated with fungus spores has been reported to lead to pulmonary aspergillus infections in immunocompromised patients, and sharing of marijuana water pipes has been associated with transmission of tuberculosis.