Exhibit 5.1 LATHROP & GAGE L.C. LAW OFFICES 2345 Grand Boulevard 1050/40 Corporate Woods Suite 2800 9401 Indian Creek Parkway Kansas City, Missouri 64108-2684 Overland Park, Kansas 66210-2007 816-292-2000, Fax 816-292-2001 913-451-5100, Fax 913-451-0875 JOHN H. CALVERT 816-460-5807 jcalvert@lathropgage.com or 72741.3656@compuserve.com _______, 1999 Board of Directors Lab Holdings, Inc. 5000 West 95th Street Shawnee Mission, Kansas 66207 Re: Offering by Lab Holdings, Inc. (the "Company") of shares of Common Stock, $0.01 par value (the "Common Stock") pursuant to that certain Agreement and Plan of Merger by and between Lab Holdings, Inc. and LabOne, Inc. as amended and restated, dated as of March 7, 1999 (the "Merger Agreement"), a copy of which is appended to the Joint Proxy Statement/Prospectus that has been filed with the Securities and Exchange Commission as a part of the registration statement of the Company on Form S-4, file No. 333-_____ (the "Registration Statement"). Gentlemen, We have acted as counsel to the Company in connection with the above referenced Offering pursuant to which the Company proposes to issue shares of its Common Stock to the holders of common stock of LabOne, Inc. in accordance with the terms of the Merger Agreement. We have examined the Merger Agreement, the Articles of Incorporation and Bylaws of the Company, as amended, the proceedings of the Board of Directors of the Company in connection with the authorization, execution and delivery of the Merger Agreement and the filing of the Registration Statement, certificates of officers of the Company and of state officials and such other documents as we have deemed necessary in order to express the opinion set out herein. As to certain questions of fact material to our opinion we have, without independent investigation, relied upon the representations and warranties of the parties as set forth in the Merger Agreement. We have also assumed the genuineness of all signatures on original documents and certificates examined by us. Our opinion is limited to the matters expressly set forth herein, and no opinion is to be implied or may be inferred beyond the matters expressly so stated. Our opinion is also limited to the effect of the laws of the state of Missouri and the Federal laws of the United States. We express no opinion with respect to the effect of the laws of any other jurisdiction on the matters referred to herein. We further disclaim any obligation to update this opinion letter for events occurring after the date of this opinion letter. Based upon the foregoing, and assuming that (i) the Merger Agreement is approved by the holders of the requisite number of shares of capital stock of the parties thereto, (ii) that all conditions to the Merger Agreement are either satisfied or properly waived, and (iii) that the Merger Agreement is properly filed with and certificates of merger with respect thereto are duly issued by the Secretaries of State of Missouri and Delaware, all as contemplated by the Merger Agreement, we are of the opinion that the Common Stock, when issued to the Board of Directors Lab Holdings, Inc. ______________, 1999 Page 2 stockholders of LabOne pursuant to the Merger Agreement, will be duly authorized, legally issued, fully paid and non-assessable. We consent to the use of this opinion in the Registration Statement and in pre-effective and post-effective amendments thereto. We also consent to the use of this opinion and to the reference to our firm under the caption ("Legal Opinions") in the Joint Proxy Statement/Prospectus of the Registration Statement and amendments thereto. Very truly yours, LATHROP & GAGE L.C. By: John H. Calvert