1 EXHIBIT 5.1 May 20, 1998 Aspect Telecommunications Corporation 1730 Fox Drive San Jose, CA 95131-2312 REGISTRATION STATEMENT ON FORM S-8 Ladies and Gentlemen: We have examined the Registration Statement on Form S-8 to be filed by you with the Securities and Exchange Commission on or about May 20, 1998 (the "Registration Statement") in connection with the registration under the Securities Act of 1933, as amended effective, of a total of 441,832 shares of your Common Stock (the "Shares") reserved for issuance under the Company's assumed Voicetek Corporation 1992 Equity Incentive Plan and the Voicetek Corporation 1996 Stock Option Plan (the "Option Plans"). As your legal counsel, we have examined the proceedings taken and are familiar with the proceedings proposed to be taken by you in connection with the sale and issuance of the Shares under the Option Plans. It is our opinion that, when issued and sold in the manner referred to in the Option Plans and pursuant to the respective agreement which accompanies each grant under the Option Plans, the Shares will be legally and validly issued, fully paid and nonassessable. We consent to the use of this opinion as an exhibit to the Registration Statement and further consent to the use of our name wherever it appears in the Registration Statement and any amendments to it. Sincerely, VENTURE LAW GROUP A Professional Corporation /s/ VENTURE LAW GROUP