In Korea the infectious diseases inciuding tuberculosis are still a major factor of morbididy and mortality in diabetics. High prevalence af infect.ions are probably associated with undernutrition and underweight. To evaluate the prevalences and risk factors of infec- tious diseases, we studied 434 patients with diabetes mellitus from Jan, l984 to Jun, 1986, The following results were obtained. 1) Among 434 patients, the prevalence of infectious diseases including tuberculosis was 26.7% and the rate was highest in underseight NIDDM (56.0%) according the types (p<0.01). 2) The prevalence af tuberculosis was 10.1% and the rats was highest in underweight NIDDM (28.0%) (p<0. 01). It was inversely correlated to the body weight of the patients. 3) The prevalence of other infections was 19.6% and the rate was highest in underweight NIDDM (32.0%), too (p<0.05). 4) E. Coli (42.4%), Klebsiella, Acinetobactor, Staphylacoccus epidermidis (9.1%), Pseudomonas, fungus (6. 1%) were major isolated organisms in urinary tract infections and monilia (42.9%) was the most frequently isolated organism in vaginitis.