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1. We examined the functional morphology of the intra‐ocular muscles of the grey squirrel using pharmacological and histological methods. Using sympathomimetic (phenylephrine) and parasympathomimetic (carbachol) agents, administered by transcorneal iontophoresis, the response of the iris sphincter and dilator muscles and the ciliary muscle were recorded. Measurement techniques included both streak retinoscopy and coincidence optometry for measurement of ocular refraction and high resolution ultrasonography to monitor changes in the intra‐ocular component dimensions. 2. The grey squirrel was found not to possess a functional accommodative system. No change in ocular refraction or intra‐ocular dimensions could be induced with 40% carbachol. Marked changes in pupil diameter occurred with topical application of both phenylephrine (dilation) and carbachol (constriction). Histological findings were …