Psoriasis is a chronic, immunologically based inflammatory skin disease. Efalizumab (Raptiva) is a humanized monoclonal immunoglobulin G1 antibody that binds with high specificity and affinity to the alpha subunit of leucocyte function-asssociated antigen-1 (LFA-1) on the surface of T cells. Therefore, efalizumab is an effective biologic therapy for the long-term treatment of chronic moderate-to-severe plaque psoriasis. This drug demonstrated a good safety profile, whereas most adverse events were mild to moderate in severity. During efalizumab treatment, a small percentage of patients experienced protocol-defined psoriasis adverse events (e.g. worsening of psoriasis or the onset of new psoriasis morphologies). We present the case of a patient who experienced a new onset of guttate psoriasis and a mild worsening of pre-existing psoriatic lesions during treatment with efalizumab. Restarting with the same drug did not induce any adverse events.