Interspecific hybridization occurs widelyacross a taxonomically diverse array of fishspecies. Multiple factors typically interactto effect the outcome of hybridization events. Human influences have been frequently cited ascontributing factors (nearly 50% of reviewedcase studies). Aquacultural activities,species introductions, and loss or alterationof habitats were frequently implicated. Wehighlight the utility of genetic markers andnovel methods of statistical analysis forinferring the extent, rate, direction, andlikely causes of hybridization. Emphasis isplaced on cytonuclear genetic systems. Wedemonstrate the utility of cytonuclear modelsfor hypothesis testing using empirical data.