My work focuses on modelling the population dynamics of soil transmitted helminths and schistosomes. With the recent advent of large-scale donations of anthelminthic drugs from pharmaceutical companies, it is essential to understand the impact of different regimes of mass drug administration on the parasite burden of populations. In particular, how the degree of control or the possibility of elimination depend on whom the drugs are targetted at and how frequently. My work involves analysis of simple mathematica models as well as simulation using age-structured models and stochastic individual (worm) based approaches. Helminths are characterised by a high degree of variability in their distribution among hosts and reproductive behaviour and the techniques of data collection are also prone to error. My aim is to develop Baysian techniques to properly integrate parameter and biological uncertainty into the models and hence give realistic confidence intervals on model output.