In Europe, tick-borne diseases are the most important group of vector-borne diseases (Heyman et al. 2011; Randolph 2001; Randolph and Šumilo 2007). Research focus has long been on Lyme borreliosis and tick-borne encephalitis (TBE), because of their prevalence and public health impact. However, recently, new pathogens have emerged or re-emerged and geographical distributions of pathogens are changing. Also new techniques and developments in statistical and mathematical modelling have become available which allow for more accurate identification of risk areas as well as for conducting scenario studies. This special issue aims at bringing together some of the latest results on (re)emerging tick-borne diseases and putting them in the perspective of the trends and developments in the ever-changing research field of tick-borne pathogens, with emphasis on the European continent. We see that for some disease systems, such as louping ill, TBE and Lyme disease, intensive studies over the last decades have increased our understanding of the relationship between population dynamics of the various tick-host species, tick populations and pathogen transmission. This is much less the case for other pathogens, including many emerging pathogens, and these knowledge gaps still have to be filled in order to obtain a true understanding of the role of population dynamics, land use, changes in climate, etc. Knowledge and understanding of the underlying mechanisms driving the dynamics of these complex disease systems are of vital importance if we want to minimize the burden of tick-borne diseases now and in the future.