Fecundity of guchibaim, Mastacembelus pancalus was described based on 100 samples collected from the experimental ponds of the Field Laboratory Complex, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh during the period from May to July 2007. The surveyed sample ranged from 115 to165mm in total length and 6.97±0.44 to 10.52±0.22g in average body weight. The ovary weight of the specimens varied from 0.77±2.61 to 5.19±0.29g. The fecundity was found to vary from 881.50±44.03 to 1182.30±27.33 eggs. The relationship between fecundity and total length was linear and it was expressed as: Y= 4.3927x+398.02 (R2=0.5336). The relationship between fecundity and body weight was linear and it was expressed as: Y= 67.319x+449.62 (R2=0.7446). The relationship between fecundity and ovary weight was also linear and it was expressed as: Y=72.36x+799.77 (R2=0.9189). The fecundity was highly correlated with the total length, body weight and ovary weight of fish and the Mastacembelus pancalus is a low fecund fish.