Objective To explore the severity of toxicity reaction after treated by the sequential chemoradio-therapy,alternate chemoradiotherapy or concurrent chemoradiotherapy in limited -stage small cell lung cancer. Methods 63 cases of limited -stage small cell lung cancer were reviewed,according to the chemoradiotherapy order,all cases were divided into:sequential chemoradiotherapy 15 cases,alternate chemoradiotherapy 25 cases, concurrent chemoradiotherapy 23 cases.The correlation of the factors(leukocypenia,gastrointestinal reaction,pneumo-nia,esophagitis)with different treatment groups after treated in 2 months,4 months,6 months were analyzed.Results Three groups of all the factors treated in 2 months had no significant change(χ2 =0.275,0.051,0.513,1.215, 0.051,0.231,all P >0.05).In 4 months the cases of sequential chemoradiotherapy >or =2 myelosuppression,the gastrointestinal reaction,the pneumonia and the esophagitis were 33.3%,33.3%,0.0%,0.0%;In the cases of alternate chemoradiotherapy >or =2 myelosuppression,the gastrointestinal reaction,the pneumonia and the esophagitis were 16.0%,4.0%,16.0%,0.0%;In the cases of concurrent chemoradiotherapy >or =2 myelosuppression,the gastroin-testinal reaction,the pneumonia and the esophagitis were 52.2%,34.8%,34.8%,4.3%;>or =2 myelosuppres-sion,each level gastrointestinal reaction and the pneumonia of the three groups treated were statistically significant (χ2 =7.054,9.702,7.947,6.145,7.373,all P or =2 myelosuppression,the gastrointestinal reaction,the pneumonia and the esophagitis were 26.7%,13.3%,13.3%, 0.0%;In the cases of alternate chemoradiotherapy >or =2 myelosuppression,the gastrointestinal reaction,the pneu-monia and the esophagitis were 40.0%,56.0%,12.0%,0.0%;In the cases of concurrent chemoradiotherapy >or =2 myelosuppression,the gastrointestinal reaction,the pneumonia and the esophagitis were 69.6%,65.2%,43.5%,0.0%;each level myelosuppression,>or =2 gastrointestinal reaction and the pneumonia of the three groups treated were statistically significant(χ2 =6.174,7.663,10.544,6.286,all P <0.05).Conclusion Leukopenia and gastrointestinal reaction are closely related with chemotherapy,chemoradiotherapy results in the worsen of myelosuppression.Pneumonia and esophagitis are closely related with chemotherapy,chemoradiotherapy result in the worsen of radiation pneumonitis.