PURPOSE: To compare biochemical and haematological characteristics of underground mine-workers with EAMC with a control group of non-cramping mine workers after a work shift. METHODS: Retrospective descriptive haematological and biochemical profiles of underground mine workers who presented with EAMC over 18 months in a South African gold mine (CRA group) was compared with a prospective control group of similar workers without EAMC from which data were collected before (CONPRE) and after (CONPOST) 8 hour shifts. Despite the large number of CRA participants, some data were non-parametric. Results were summarized using medians and percentiles where appropriate. For comparison of categorical variables, the Chi2 and Fisher-exact tests were used. 95% confidence intervals indicated significant differences between the medians of paired scale data sets. RESULTS: Significant differences between the CRA group and the CONpost group showed signs of dehydration (increased haematocrit and haemoglobin; p<0.001), inflammation (elevated total white cell count; p<0.001), elevated urea and creatinine (p<0.001), and lower fluid intake (p<0.001). Serum sodium and chloride levels were not significantly different between the CRA and CONpost groups. Muscle damage was indicated by elevated but similar (p=0.2) creatine kinase (CK) and in both the CRA and CONpost groups. The most important finding was significantly higher serum myoglobin in the CRA group compared to the CONpost group (median of 51ng/ml compared to 186.5 ng/ml; p<0.001). CONCLUSION: EAMC is associated with elevated inflammatory markers, dehydration and hemoconcentration, elevated creatinine and protein levels. If corrected for dehydration, reduced serum chloride and sodium levels may be shown. Significantly higher s-myoglobin levels in miners with EAMC compared to a control group indicate an association between muscle damage and EAMC. Further investigation into the pathogenesis of EAMC will be guided by these results.