This paper examines the use of zero truncated models for the estimate of the population size of fake drug Syndicates in Onitsha, Southeast Nigeria. Various estimators under zero-truncated Poisson models and geometric models were used to estimate this kind of hidden population. The estimators are Maximum Likelihood, Turing, Chao's Lower Bound and Zelterman. The weighted estimators for the four candidate estimators under zero-truncated Poisson model gives the population size of fake drug Syndicates as 6579. As 1434 were observed, this means that only about 22% of these Syndicates are observed with 95% confidence interval of 19%-25% leaving about 78% unobserved still in the distribution chain of this drugs. Similarly, the weighted estimator for the four candidate estimators under zero-truncated geometric model is 12649 with only about 11% of the population being observed with confidence interval of 10%-13%, leaving about 89% still in the distribution chain. This is not good news for National Agency for Food and Drug Administration and Control (NAFDAC), the agency responsible for checkmating illicit and counterfeits drugs in Nigeria. The study also shows that of all the offense committed by fake drug Syndicates, falsification of genuine drugs was rampantly committed, followed by the selling of expired drugs, while the least committed offense was the selling of banned drugs