Purpose: Retinoblastoma is the most frequent primary intraocular tumour and is rapidly gaining importance in Asia. As the survival is markedly dependent on early diagnosis and as information on that is not available from East Asia, we assessed the time interval between symptoms detection and therapy of children treated in the Beijing TongRen Eye Hospital. Methods: The retrospective study consisted of all patients who were treated in the study period from January 1987 to November 2006 in the Beijing TongRen Hospital and for whom the data on delay in diagnosis, age, clinical appearance and histological tumour features were available. Results: The inclusion criteria were met by 572 patients (326 boys) with a mean age of 2.6 +/- 1.8. Mean interval between first detection of symptoms and clinical diagnosis and therapy was 4.1 +/- 5.9 months (range: 3-36 months). A diagnostic delay of 2 months or >6 months was found for 337 (59%) children and 98 (17%) children, respectively. Diagnostic delay was significantly (p < 0.001) the longest in the 2-to 4-year-old group (5.5 +/- 7.4 months). It decreased from the study period 1987-1991 to the period 2002-2006 (p < 0.001). It was significantly associated with the clinical appearance (p = 0.001) and histological finding (p = 0.008). Conclusions: Delay in the diagnosis of retinoblastoma depended on the age of the children, study period, and clinical and histological stage. Because the prognosis is markedly influenced by tumour stage, further improvements in the alertness of parents, family doctors and paediatricians and in the medical infrastructure in China may be addressed.