The authors consider the oscillation behavior of the delay differential equation \[ x'(t)+p(t)x (t-\tau(t))=0 \] with \(p,\tau\in C([0, \infty), [0,\infty))\), \(t-\tau(t)\) is increasing, and \(\lim_{t\to\infty}(t-\tau (t))= \infty\). It is shown that the equation is oscillatory if \(M+{L^2\over 2(1-L)}+ {L^2\over 2}\lambda_0 >1\) where \[ L=\lim \inf_{t\to \infty} \int^t_{t-\tau (t)}p(s)ds, \quad M=\lim \sup_{t\to \infty} \int^t_{t-\tau (t)}p(s)ds, \] and \(\lambda_0\) is the smaller real root of the equation \(\lambda= e^{L\lambda}\). This result allows \[ \lim\inf_{t\to\infty} \int^t_{t-\tau (t)}p(s) ds\leq 1/e. \]