Confocal microscopy was used to investigate the temporal and spatial properties of Ca²⁺ transients and Ca²⁺ sparks in ventricular myocytes of the rainbow trout (Oncorhynchus mykiss). Confocal imaging confirmed the absence of t-tubules and the long (~160 µm) thin (~8 µm) morphology of trout myocytes. Line scan imaging of Ca²⁺ transients evoked by electrical stimulation in cells loaded with Fluo-4 revealed spatial inhomogeneities in the temporal properties of Ca²⁺ transients across the width of the myocytes. The Ca²⁺ wave-front initiated first, rose faster and reached larger peak amplitudes in the periphery of the myocyte compared with the centre. These differences were exacerbated by stimulation with the L-type Ca²⁺ channel agonist (-) Bay K 8644 (Bay K) or by sarcoplasmic reticulum (SR) inhibition with ryanodine (Ry) and thapsigargin (Tg). Results reveal the shape of the trout myocyte allows for rapid diffusion of Ca²⁺ from the cell periphery to the cell centre with SR Ca²⁺ release contributing to the cytosolic Ca²⁺ rise in a time-dependent manner. Spontaneous Ca²⁺ sparks were exceedingly rare in trout myocytes under control conditions (1 sparking cell from 238 cells examined). This is in marked contrast to the rat where a total of 56 spontaneous Ca²⁺ sparks were observed in 9 out of 11 myocytes examined. Ca²⁺ spark-like events were observed in a very small number of trout myocytes (15 sparks, from 9 cells out of 378 cells examined) after stimulation with either Bay K or high Ca²⁺ (6 mM). Reducing temperature to 15 °C in intact myocytes, or permeabilising myocytes to adjust intracellular conditions to favour Ca²⁺ spark detection were without significant effects. Possible reasons for the rarity of Ca²⁺ sparks in a cardiac myocyte with an active SR are discussed.