Solid controlled-release oral dosage forms comprising a therapeutically effective amount of an opioid analgesic or a salt thereof which provide an extended duration of pain relief of about 24 hours, have a dissolution rate in-vitro of the dosage form, when measured by the USP Paddle Method of 100 rpm in 900 ml aqueous buffer at 37.degree. C. from about 12.5% to about 42.5% (by weight) active agent released after 1 hour, from about 25% to about 55% (by weight) active agent released after 2 hours, from about 45% to about 75% (by weight) opioid analgesic released after 4 hours and greater than about 60% (by weight) opioid analgesic released after 8 hours, the in-vitro release rate being substantially independent of pH and chosen such that the peak plasma level of active agent obtained in-vivo between about 2 and about 8 hours after administration of the dosage form.