Parexel International Corp. posted third-quarter sales of $311 million, up 5.5 percent compared with $294.7 million during the same period last year.

Net income for the Waltham-based contract research organization was flat at $14.2 million for the quarter, compared with $14.19 million during the third quarter of 2008.

Total sales included $264.5 million in service revenues and $46.5 million in reimbursement revenues. Parexel said the service revenues included $199.7 million for its clinical research services segment, $29.2 million for its consulting and medical communications services arm and $35.6 million from Perceptive Informatics Inc., its IT subsidiary.

The company said it expects fourth-quarter sales of as much as $277 million (excluding reimbursement revenues) and up to $1.08 billion for the full year.