The aim of this paper was to investigate the frequency of echocardiography (ECHO) and pulmonary function test (PFT) abnormalities in childhood onset systemic lupus erythematosus (SLE), and to determine the relationship of these abnormalities to disease activity. The charts of 50 patients with childhood onset SLE attending a pediatric rheumatology clinic were reviewed for ECHO and PFT studies. The frequency and description of ECHO and PFT abnormalities were documented. Possible associations of PFT and ECHO abnormalities with clinical cardiopulmonary disease, radiographic findings, and measures of lupus disease activity were evaluated. Forty patients (80%) had at least one ECHO study. Twenty-seven (68%) had an abnormal initial study. Nine of 14 patients with an initial abnormal ECHO had normal findings on repeated study. Three abnormalities were considered moderately severe. Thirty-three patients (66%) had at least one PFT performed. Sixteen (48%) were abnormal initially. Four of these 'abnormal' studies were repeated and the abnormalities persisted. Nine patients (27%) were considered to have a severe abnormality. Thirty-one children (62%) had both studies performed. An initial abnormal ECHO and abnormal PFT was found in 10 (32%) of these children. No relationship between ECHO or PFT abnormality and any measure of disease activity (physician's global assessment, anti DNA, C3 or ESR) could be found. Occult cardiac and pulmonary disease as demonstrated by ECHO or PFT occurs frequently in childhood onset SLE. If we wish to understand the natural history of these abnormal heart and lung findings, it will be necessary to do serial testing with ECHO and PFTs in this population.