This paper presents methods for initial investigation of occupational cancer clusters using limited data. Phase 1 of the methods developed uses basic data from the cluster of cases, but with cohort data limited to the size of the workforce at the plant. Phase 2 of the methods requires knowledge of the number of workers entering and leaving the workforce in each year. In the absence of data concerning age, the spreadsheet programs explore a variety of worker age distributions in synthetic cohort analyses. The methods were used to assess a cluster of six cases of leukemia with an average duration of work of 11 years in a tire manufacturing plant. It was concluded that the relative risk for the age range 30-50 was at least 7, providing further evidence for the association of leukemia with work in tire manufacture. The use of spreadsheet programs can provide a valuable first step assessment of apparent workplace cancer clusters.