The asian tiger mosquito Aedes albopictus (Skuse) has spread rapidly in Europe, the Middle East, Africa and the Americas in the last few decades and from a public health standpoint, it deserves special attention, being an efficient vector of viruses that can cause disease in humans and other animals. In last decades scientists have given theoretical attention to Wolbachia, a bacterium (Ricketsiales) among the most widespread intracellular bacteria, carried by an estimated 15-76% of insect species among these Ae. albopictus. The most common reproduction manipulation imposed by the bacterium to its hosts is a form of conditional male sterility known as cytoplasmic incompatibility (CI). CI is a phenomenon of non-viability of embryos resulting from mating of uninfected females with infected males or mating between males and females harbouring different Wolbachia strains. Ae. albopictus is reported to be uniformly superinfected with two Wolbachia strains (wAlbA and wAlbB) throughout its geographical distribution. This symbiosis is characterized by strong level of CI observable in crosses between females of artificial aposymbiotic lines and wild infected males, high efficiency in maternal transmission and benefits to fitness of infected females. If from one hand this traits are a basic account to understand the fixation of this Wolbachia infection profile, from the other hand, they represent a limit for using CI as tool in vector control strategies based on incompatible male releases, since no evidence of crossing type polymorphism has been reported. In order to exploit CI as source of sterility in Ae. albopictus for IIT (Incompatible Insect Technique) purposes we have successfully obtained a new Ae. albopictus line, by removing the natural Wolbachia infection and transferring into the obtained aposymbiotic line an exogenous Wolbachia straintaken from Culex pipiens molestus, phylogenetically quite close to the wAlb B strain. The trans-infected strain (ARwP line) showed high rates of unidirectional and bidirectional CI ( 100%). This represents an excellent example in which an exogenous strain of Wolbachia imposes the same phenotype alteration (strong CI) on native and new hosts (Calvitti et al., 2010). Maternal inheritance of the wPip infection is highly effective ( 100%) and also survival of both immature and adult stages of the ARwP line was not found to significantly differ in comparison with wild Ae. albopictus. Since in nature Wolbachia can range from parasitic to symbiotic, depending upon the interaction with host species we expected that new Wolbachia-host associations created by trans-infection experiments, differently from those resulted from a long-term host-symbiont coevolution, could result in female fitness costs (reduced growth rate capacity). In fact, ARwP female fitness was significantly affected by the new infection, in terms of reduction of female fecundity and egg fertility. Anyway, our experience on ARwP Ae. albopictus tells us that this fitness cost has been going to be attenuated (in particular with regard to female fecundity) by consecutive selection (Calvitti et al., unpublished data) ensuring ease of mass rearing even maintaining very strong CI and maternal transmission. While it seems established that Wolbachia infection affect female fitness in Ae. albopictus, for males the issue is more controversial and need further study. Because Wolbachia is transmitted exclusively through female hosts some authors are inclined to assume that males are an evolutionary dead end in terms of Wolbachia infection (Dobson et al. , 2004), and that no direct selection by Wolbachia is theoretically expected on male fitness. In this work we intend to give a contribution to the knowledge of the effect that a Wolbachia infection artificially established causes on male fitness. We focused our study on the reproductive biology of trans-infected Ae. albopictus in comparison with naturally superinfected males. To do this, we have performed experiments ranging from fertilization capacity to sperm transfer quantification and mating competitiveness.