BACKGROUND AND AIMS: In most hospitals in Vietnam, clinical assessment of nutritional status has yet to become part of the routine clinical history taking and physical examination. It is the aim of this study to apply subjective global assessment (SGA) of nutritional status in surgical patients in the Mekong Delta, Vietnam, to determine the incidence of malnutrition according to SGA and to know whether there was an association between SGA class and infectious complications. METHODS: A prospective, cross-sectional study design was used. SGA of nutritional status was applied. Patients were rated as well nourished (A), moderately malnourished (B) or severely malnourished (C). Infectious complications (wound infection, intra-abdominal abscesses, anastomotic leakage) were recorded. RESULTS: Of the 438 patients assessed, 194 (44.3%) were classified as A, 126 patients (28.8%) were classified as B and 118 patients (26.9%) were classified as C. Of the 274 patients who underwent major abdominal surgery assessed, 61 patients (22.3%) were classified as A, 97 patients (35.4%) were classified as B and 116 patients (42.3%) were classified as C. Weight loss and percent weight loss, muscle wasting, loss of subcutaneous fat, functional capacity and significant gastrointestinal symptoms correlate significantly with the severity of SGA class (P<0.001). The rate of postoperative infectious complications was higher in patients classified as SGA class C (33.6%) than as class A (6%) and B (11%). CONCLUSIONS: A high rate of malnutrition was found, applying SGA of nutritional state in surgical patients in Vietnam. Malnutrition was associated with an increase in infectious complications. Special attention should be paid to weight loss, muscle wasting, loss of subcutaneous fat, functional capacity and gastrointestinal symptoms.