Also the Gerdes Site has info like this:
David W. Carroll, captain of Company A, was appointed colonel; John N. Daly, a private in Company I, was appointed lieutenant-colonel; and Robert Hamilton Crockett, a private in Company E, was appointed major. The new regiment got off to an inauspicious, indeed, a tragic start. Measles broke out among the men almost immediately, and by the time the regiment arrived at its assigned station at Fort Pillow, near Fulton, Tennessee, it had become a full-fledged epidemic. It is possible to track the movements of the regiment in April 1862 by following the bodies. The unfortunate soldiers of the 18th Arkansas were dropping like flies, and every camp between DeValls Bluff and Fort Pillow contained the graves of those who had died during the night. At Fort Pillow, the regiment was literally decimated by the epidemic. By the time the epidemic had run its course, over a fourth of the men were dead, discharged or simply stricken from the rolls. The regiment was forced to undergo a major reorganization in June 1862, to replace the vacant commissioned and non-commissioned officer slots. Colonel Carroll was forced to resign due to illness, and was succeeded by Lieutenant-Colonel Daly.

With the epidemic behind it, the 18th Arkansas was ordered to Corinth, Mississippi, where it was assigned to Colonel Thomas Pleasant Dockery’s 2nd Brigade, Army of the West, along with the 19th, 20th and 21st Arkansas regiments, and the 8th Arkansas battalion. The 18th Arkansas fought in the battle at Iuka Springs, Mississippi, September 16, 1862, and then ensured its place in history at the battle of Corinth, Mississippi, October 4, 1862. From all contemporary accounts, the 18th Arkansas performed with magnificent courage at Corinth. Mustering a little over 300 men on the morning of the battle, only 43 answered the roll at the end of the day. Forming in a line of battle, the 18th Arkansas made a breath-taking charge under an enfilading fire from the entrenched Federal troops. Climbing through and over fallen timber, the 18th Arkansas relentlessly advanced right up to the enemy’s breastworks, where the withering fire literally melted the regiment away. Colonel Daly, leading the charge, sword in hand, was mortally wounded. Captain Parish, of Company H, immediately assumed command and rallied the regiment to continue the charge. Although he, too, was shot down, he survived the battle and received a meritorious promotion to lieutenant-colonel for his gallant conduct.

Following the battle of Corinth, the 18th Arkansas and its sister regiments of the 2nd Brigade were ordered to Port Hudson, Louisiana, where they formed a part of the garrison there, and endured the siege of that place. The garrison finally capitulated on July 9, 1863. The enlisted men were paroled on July 12, but the officers were sent to military prisons in the North for the rest of the war. Two audacious lieutenants of Company K, however, James W. Hellums and George P. Atkins, escaped from their captors by jumping from the Union transport into the muddy water of the Mississippi River between Napoleon and Helena, swam ashore, and eventually reached the Confederate lines.

There are few records of the 18th Arkansas after the fall of Port Hudson. The remnants of the regiment reorganized in southwest Arkansas, but were eventually consolidated with the remnants of the 23rd Arkansas and other Port Hudson units to form the 2nd Arkansas Consolidated Regiment. They spent the remainder of the war in the Trans-Mississippi Army, and were included in the general surrender of that army on May 26, 1865, at Marshall, Texas.

http://www.couchgenweb.com/civilwar/18thhis.html