During 1967, 1968 and 1969, blood samples were taken from 83 cows affected by parturient paresis. Whole blood glucose estimations were made on these samples. The range was 1.33 to 10.22 mmol/1 with an average of 3.94 mmol/1. Eighteen cows known to have been affected less than 4 hours had average levels of 3.06 +/- 1.11 mmol/1. All (except one) "previously untreated" cows with levels less than 3.33 mmol/1 were on their feet within 10 minutes whereas cows with higher levels than this had a 28.6% delayed recovery rate. The evidence suggests that low levels have no clinical significance but that higher levels are significant in that they occur as a result of prolongation of attacks of parturient paresis.