Male infertility is a common disease with implications beyond an inability to conceive a child, affecting approximately 7% of men in the Western world. Most male infertility is idiopathic in origin, meaning many men go without an accurate diagnosis and thus precise treatments cannot be provided. Further, infertile men as a cohort die younger than their fertile counterparts, suggesting that conserved mechanisms required for male fertility play roles in other tissues. Despite its unknown aetiology, it is estimated that genetic causes are responsible for up to 40-50% of all male infertility cases. We therefore set out to investigate the effect of mutations in single genes that lead to male infertility. Ongoing genetic screens performed on infertile versus fertile men have identified (and are continuing to identify) pathogenic mutants in potential male fertility genes. An initial whole exome screen on azoospermic infertile males has highlighted 10 genes that have been assessed for their role in male fertility, by means of a Drosophila RNA interference system screen. For each candidate gene, RNA interference has been performed to target expression in the germline (nanos-enhancer) or somatic (traffic jam-enhancer) lineages of the testis, independently, utilising 1-4 available RNAi lines commercially available. While many of these genes were proven to be dispensable for male fertility, one heat shock protein gene (HSPA4L) has shown a pivotal role in early germ cell development, with knockdown resulting in male sterility and abnormal testis histology. Such effects were absent when HSPA4L was ablated in the somatic lineage of the testis. This sterility in germ cell derived knockdown of expression was validated in two independent fly lines targeting HSPA4L, highlighting a severe reduction in testis size. Further study is focusing on understanding this loss of fertility, hypothesised to be due to a maturation arrest during spermatogenesis.