Caspofungin, a semisynthetic derivative of the pneumocandin B(0), is the first licensed compound of a new class of antifungal agents, the echinocandins. It attacks the fungal cell by selective inhibition of the beta-(1,3)-d-glucan synthase, which is not present in mammalian cells. In vitro studies have indicated a potent fungicidal effect on Candida species, and in vivo studies in immunocompromised animals with invasive candidiasis demonstrated a favourable outcome. In randomized clinical trials in patients with oropharyngeal/oesophageal and invasive candidiasis, caspofungin was at least as effective as amphotericin B deoxycholate, yet showed a significantly superior safety profile. Of patients with invasive aspergillosis refractory to or intolerant of other antifungal agents, 45% showed a partial or complete response to caspofungin given as a salvage treatment. Also, it demonstrated comparable clinical efficacy but superior tolerability in the empirical antifungal therapy in neutropenic patients compared with liposomal amphothericin B. Caspofungin has an excellent tolerability and a low potential for drug interactions. Thus, caspofungin represents an interesting and clinically valuable new antifungal drug that broadens the available therapeutic armamentarium for the treatment of invasive fungal infections.