The paper addresses the issue of making Virtual Humans unique and typical of some (social or ethnical) group, by endowing them with style. First a conceptual framework of defining style is discussed, identifying how style is manifested in speech and nonverbal communication. Then the GESTYLE language is introduced, making it possible to define the style of a VH in terms of Style Dictionaries, assigning non-deterministic choices to express certain meanings by nonverbal signals and speech. It is possible to define multiple sources of style and maintain conflicts and dynamical changes. GESTYLE is a text markup language which makes it possible to generate speech and accompanying facial expressions and hand gestures automatically, by declaring the style of the VH and using meaning tags in the text. GESTYLE can be coupled with different low-level TTS and animation engines.