OBJECTIVE: To investigate the effects of the Gln27Glu polymorphism of beta2-adrenergic receptor (beta2AR) on serum lipid and apolipoprotein ratios and its interaction with high-carbohydrate/low-fat (HC/LF) diet on the ratios in healthy youth. METHODS: After on a washout diet for seven days, fifty six healthy young subjects were given the HC/LF diet for six days. The 12 hour-fasting serum lipids and apolipoproteins (apo) AI and B100 were measured on the 1st, the 8th and the 14th days. The ratios of TG/HDL-C, log (TG/HDL-C), TC/HDL-C, LDL-C/HDL-C and apoAI/apoB100 were calculated. The polymorphism of Gln27Glu was analyzed by PCR-RFLP method. RESULTS: No significant differences were found of the lipid and apolipoprotein ratios at baseline and before the HC/LF diet between the subjects with the CC genotype (wide type) and the G carriers (mutation carriers) in the whole study sample or the males and the females separately. The G carriers had a significantly higher level of log (TG/HDL-C) (P=0.038) than the subjects with the CC genotype did after the HC/LF diet in the whole study sample but not in the males and the females separately. Significant decreases of LDL-C/HDL-C and TC/HDL-C were observed in all the subjects after the HC/LF diet when compared with those before the HC/LF diet (P<0.05), but a significant increase of apoAI/apoB100 (P=0.021) only in the subjects with the CC genotype. When gender was taken into account, significant decreases of LDL-C/HDL-C and TC/HDL-C were found after the HC/ LF diet in the male subjects regardless of genotypes (P<0.05). Significant increases of TG/HDL-C and log (TG/ HDL-C) and a significant decrease of TC/HDL-C were found in all the female subjects (P<0.05), while a significant decrease of LDL-C/HDL-C (P=0.037) was only observed in the female subjects with the CC genotype. CONCLUSION: The G allele of beta2AR Gln27Glu variation can inhibit the decrease of LDL-C/HDL-C in females after HC/LF diet intervention.