Investment funds allocated to speculative activity. Risk capital refers to funds used for high-risk, high-reward investments such as junior mining or emerging biotechnology stocks. Such capital can either earn spectacular returns over a period of time, or may dwindle to a fraction of the initial amount invested if several ventures prove unsuccessful. Diversification is key for successful investment of risk capital. In the context of venture capital, risk capital may also refer to funds invested in a promising start-up.