Earlier we have reported the antidiabetic activity of fresh juice of rhizomes of Zingiber officinale (Z. officinale) and its correlation with 5-HT receptor antagonism. Since 6-gingerol the marker compound of Z. officinale is reported to posses 5-HT anatgonistic activity, the present investigation, was undertaken to find out the concentration of 6-gingerol present in methanolic extract of Z. officinale and its different fractions (petroleum ether, toluene and chloroform). We also evaluated these fractions for antidiabetic activity in streptozotocin (STZ)-induced neonatal type 2 diabetic rats. Fasting glucose and insulin levels in non insulin dependent diabetes mellitus (NIDDM) rats were found to be significantly (P < 0.05) higher than control rats and these were significantly decreased by treatment with methanolic extract of Z. officinale and its fractions. The results of oral glucose tolerance test (OGTT) showed that methanolic extract and its fractions significantly (P < 0.05) decreased both STZ-induced increase in $AUC_{glucose}$ and $AUC_{insulin}$ values in NIDDM groups. Treatment with petroleum ether fraction produced a greater reduction in elevated glucose and $AUC_{glucose}$ levels as compared to treatment with other fractions. Treatment with methanolic extract of Z. officinale and its fractions also produced significant reduction in the elevated lipid, serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) levels in NIDDM rats. The effect of petroleum ether fraction on elevated lipid, SGOT and SGPT levels was significantly greater as compared to treatment with other fractions. The concentration of 6-gingerol was found to be maximum in petroleum ether fraction (11.430%) and minimum in chloroform fraction (0.973%). The methanolic extract and toluene fraction was found to contain 3.080% and 2.191 %, 6-gingerol respectively. In conclusion, our data suggest that methonolic extract and its fractions possess significant antidiabetic activity in NIDDM rats. The extent of activity appears to be dependent on the concentration of 6-gingerol present in the extract or its fractions.