Opportunistic infections in neurology patients on long term immunosuppression are a rare but significant risk. Following three confirmed cases of pneumocysitis carinii pneumonia (PCP) in myasthenic patients on immunosuppression we undertook a review of the incidence of opportunistic infection requiring hospital admission in 62 patients with confirmed myasthenia gravis. 15% of myasthenic patients required hospital admission for treatment of opportunistic infection, community acquired pneumonia being the most common. Guidance exists for prophylaxis against PCP infection in non-HIV patients in both rheumatology and respiratory specialities. However, there is no formal guidance for neurology patients requiring long term immunosuppression. A cochrane review of randomised control trials of PCP prophylaxis in immunocompromised patients without HIV infection suggested that PCP prophylaxis is warranted in patients receiving 20 mg or more of prednisolone daily for at least one month who also have another cause of immunosuppression. Of our analysis of 62 patients with myasthenia gravis 94% received a course of prednisolone with 89% also receiving a steroid sparing agent. A significant number of patients remain on 20 mg prednisolone per day for at least one month and a co-prescribed steroid sparing agent (azathioprine, mycophenolate, ciclosporin or methotrexate). We aim to promote discussion amongst neurologists in their current practice regarding this topic.