We evaluate potential process blanks associated with 14C measurement of microgram to milligram quantities of alkenones at NOSAMS. Two strategies to constrain the contribution of blanks to alkenone 14C dates were followed: 1) Dating of samples of known age, and 2) multiple measurements of identical samples. We show that there is no systematic contamination associated with the procedure that would bias the results of alkenone dating to either younger or older ages. Our results indicate that alkenones record 14C of ambient DIC with an accuracy of approximately 10 . A conservative estimate of measurement precision is 17 for modern samples. Alkenone radiocarbon ages are expected to be reliable within 500 years for samples younger than 10,500 radiocarbon years.